CN101572685A - Transmission device used for orthogonal frequency-division multiplexing system - Google Patents

Abstract

The invention discloses a transmitting device for an orthogonal frequency division multiplexing system, comprising: a code layer mapping unit, which divides transmitted transmission blocks into ordinary data packets and enhanced data packets, divides ordinary data packets, and enhances The data packet is segmented; the encoding and modulation unit is used to perform encoding and modulation processing on each segmentation result of the ordinary data packet and each segmentation result of the enhanced data packet; the stream mapping unit is used for each encoding and modulation result of the ordinary data packet and the enhanced data Each encoding and modulation result of the packet is reassembled; the multiple-input and multiple-output processing unit is used to perform multiple-input and multiple-output processing on each encoding and modulation result of the recombined ordinary data packet and each encoding and modulation result of the recombined enhanced data packet; The mapping unit is used to insert pilots into each MIMO processing result of the normal data packet and each MIMO processing result of the enhanced data packet according to a predetermined pilot pattern, and send them out through subcarrier resources.

Description

Transmitter for Orthogonal Frequency Division Multiplexing System

technical field

The present invention relates to the communication field, and more specifically relates to a transmitting device for an orthogonal frequency division multiplexing system.

Background technique

With the rapid development of high-speed and reliable business requirements, more and more technologies have been introduced into the field of wireless communication technology, such as multiple input multiple output (MIMO) and orthogonal frequency division multiplexing (OFDM), which are key technologies of 4G. technology. After adding MIMO to the physical layer, especially with the development of MIMO technology, various MIMO deformations have caused changes in the physical layer structure.

At present, the transmitter structure in IEEE 802.16e based on OFDM technology is shown in Figure 1. In the transmitter structure shown in FIG. 1 , the randomization processing unit first performs randomization processing on the input data block, and then performs coding debugging and symbol mapping. Wherein, the space-time coding (STC) module performs the mapping of spatial multiplexing coding to MIMO according to the type of spatial coding (such as horizontal coding and vertical coding). For horizontal coding, the situation is similar to LTE (see the analysis of LTE); for vertical coding, if there is an error in only one layer, the entire coding block needs to be retransmitted.

For example, when the encoding rate is 2, use $B=\left[\begin{array}{c}{S}_1\\ S_2\end{array}\right].$ Its characteristic is that when the encoding rate is 2, there is only one encoding block, and the control signaling and overhead are relatively small. The disadvantage is that MIMO is not well utilized during retransmission.

For example, in IEEE 802.16e, there are seven modes of hybrid automatic repeat request (HARQ). Among them, 4 are MIMO modes, and 3 are combined with coding modes. A retransmission method combined with multi-antenna HARQ-STC, which uses space-time coding to generate incremental redundancy, and the first transmission $\left[\begin{array}{c}{\mathrm{the\; s}}_1\\ {\mathrm{the\; s}}_2\end{array}\right],$ transmit on retransmit $\left[\begin{array}{c}-{\mathrm{the\; s}}_2^{*}\\ {\mathrm{the\; s}}_1^{*}\end{array}\right],$ Composed of two transfers $\left[\begin{array}{cc}{\mathrm{the\; s}}_1& -{\mathrm{the\; s}}_2^{*}\\ {\mathrm{the\; s}}_2& {\mathrm{the\; s}}_1^{*}\end{array}\right],$ The premise of performing alamouti decoding is that the channel is required to be a slow-fading channel. in odd number of transmissions $\left[\begin{array}{c}{\mathrm{the\; s}}_1\\ {\mathrm{the\; s}}_2\end{array}\right],$ even number of transfers $\left[\begin{array}{c}-{\mathrm{the\; s}}_2^{*}\\ {\mathrm{the\; s}}_1^{*}\end{array}\right],$ Two consecutive times can form the STC format. Although the multi-antenna performance is utilized, since there is only one encoding module, if only one stream (that is, any one of S1 and S2) is wrong, it needs to be retransmitted, and the other stream must also be retransmitted, and the correct information is sent once more. The performance of the second retransmission is affected, and resources need to be rescheduled at the same time, which affects the processing time of the base station.

The transmitter structure in LTE based on OFDM technology is shown in Figure 2. In the transmitter structure shown in Figure 2, the coded modules are first scrambled and modulated into a complex sequence. The modulation symbols are mapped to one or several layers through layer mapping. The mapped layers are less than or equal to the number of antenna ports. For a coding block with transmit diversity, the number of layers is equal to the number of antennas; for spatial multiplexing, the number of layers can be at most equal to the number of antenna ports, and the output vector of layer mapping is mapped to the antenna port after spatial weighting through precoding, and each antenna resource mapping to generate OFDM symbols in the time domain.

Its characteristic is that the same time-frequency block can contain one to two coding blocks (that is, two streams). In the case of two streams, each stream is independently controlled to adapt to the maximum throughput, and is mapped to various antenna ports during layer mapping, that is, the number of layers is equal to the number of antennas. Therefore, although the system is more flexible in high-level stream splitting, the code modulation order of each stream is controllable, and supports multi-user multiple-input multiple-output (MU-MIMO), its disadvantage is that the control overhead increases, and retransmission in HARQ There are several situations: 1) dual stream retransmission; 2) error stream retransmission, another stream transmits new data; 3) error stream retransmission, another stream uses multiple antennas to transmit error stream, which will affect the transmission of the original stream , that is, the original stream needs to stop transmitting.

It can be seen from the above description that the above two designs are limited to diversity or multiplexing multi-antenna structures, and considering the development of multi-antennas in the future, there may be new deformations.

This should be to make the design of the transmitter more extensive.

At the same time, since the characteristics of subframes are generally used to meet the system delay requirements, RTT is used as an index to consider system delay. For some fast services (for example, semi-static services that do not need to Transmission can speed up the retransmission delay.

Contents of the invention

In view of one or more problems described above, the present invention provides a transmitting device for an OFDM system.

The transmitting device for an OFDM system according to an embodiment of the present invention includes: a code layer mapping unit, configured to receive a transport block from a medium access control layer, and divide the transport block into a normal data packet and an enhanced data packet , and segment the normal data packet according to the first predetermined length restriction to generate multiple segmentation results of the normal data packet, and segment the enhanced data packet according to the second predetermined length restriction to generate multiple segmentation results of the enhanced data packet; the coding modulation unit, It is used to perform encoding and modulation processing on each segmentation result of the normal data packet and each segmentation result of the enhanced data packet, and generate each encoding and modulation result of the ordinary data packet and each encoding and modulation result of the enhanced data packet; the stream mapping unit is used for according to The structure of the multiple-input multiple-output processing unit reorganizes each coded modulation result of the normal data packet and each coded modulation result of the enhanced data packet; Multiple-input and multiple-output processing is performed on the result and each encoding and modulation result of the enhanced data packet after reorganization to generate each multiple-input and multiple-output processing result of the normal data packet and each multiple-input and multiple-output processing result of the enhanced data packet; and a resource mapping unit, It is used to map each MIMO processing result of the normal data packet and each MIMO processing result of the enhanced data packet to each subcarrier according to the resource allocation principle, and map the pilot pattern to each subcarrier according to the predetermined pilot pattern. On the sub-carrier, an OFDM symbol is formed by inverse fast Fourier transform, inserted into a cyclic prefix, and transmitted through the antenna unit.

Wherein, the second predetermined length limitation is related to the number of antennas and the antenna mode of the OFDM system. According to the instructions of the control signaling, the multiple-input multiple-output processing unit performs one or more combination of modes in the following ways on each coding and modulation result of the recombined normal data packet and each coding and modulation result of the recombined enhanced data packet Multiple-input multiple-output processing: space-time coding mode, precoding mode, beamforming mode. Wherein, the lengths of the segmentation results of the normal data packet are equal, and the lengths of the segmentation results of the enhanced data packet are equal.

Wherein, the code modulation unit includes: a transmission block verification unit, which is used to verify the correctness of the transmission block; a bit scrambling unit, which is used to perform scrambling processing on each segmentation result of the normal data packet and each segmentation result of the enhanced data packet , generating each scrambling processing result of the normal data packet and each scrambling processing result of the enhanced data packet; the coding processing unit is used for coding each scrambling result of the normal data packet and each scrambling result of the enhanced data packet, Generate the encoding processing result of the normal data packet and each encoding processing result of the enhanced data packet; the data interleaving unit is used to perform data interleaving processing on the encoding processing result of the ordinary data packet and each encoding processing result of the enhanced data packet to generate the ordinary data packet Each interleaving processing result of the normal data packet and each interleaving processing result of the enhanced data packet; and a modulation processing unit for mapping each interleaving processing result of the normal data packet and each interleaving processing result of the enhanced data packet into corresponding complex symbols. Wherein, the transmission block checking unit uses a cyclic redundancy check method to check the transmission block.

To sum up, the present invention provides more flexible MIMO support by further subdividing the division of transport blocks. In addition, the present invention adapts to the development trend of different MIMO systems by changing the original precoding or MIMO matrix selection into a MIMO processing unit.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

Figure 1 is a schematic diagram of the transmitter structure in IEEE 802.16e;

FIG. 2 is a schematic diagram of a transmitter structure in LTE; and

Fig. 3 is a schematic structural diagram of a transmitter according to an embodiment of the present invention.

Detailed ways

The specific implementation manners of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 3 is a schematic structural diagram of a transmitter according to an embodiment of the present invention. As shown in Figure 3, the transmitter (i.e. the transmitter) includes:

The code layer mapping unit is used to receive the transmission block from the medium access control (MAC) layer, divide the transmission block into ordinary data packets and enhanced data packets, and divide the ordinary data packets according to the first predetermined length limit to generate ordinary data Multiple segmentation results of the packet, segmenting the enhanced data packet according to the second predetermined length limit to generate multiple segmentation results of the enhanced data packet;

A coding and modulation unit, configured to perform coding and modulation processing on each segmentation result of the normal data packet and each segmentation result of the enhanced data packet, and generate each coding and modulation result of the normal data packet and each coding and modulation result of the enhanced data packet;

The flow mapping unit is used to recombine the coding and modulation results of the normal data packets and the coding and modulation results of the enhanced data packets according to the structure of the MIMO processing unit;

The multiple-input multiple-output processing unit is used to perform multiple-input multiple-output processing on each coded modulation result of the recombined ordinary data packet and each coded modulation result of the recombined enhanced data packet, and generate each multiple-input multiple output of the ordinary data packet Processing results and each MIMO processing result of the enhanced data packet;

A resource mapping unit, configured to insert pilots into each MIMO processing result of the normal data packet and each MIMO processing result of the enhanced data packet according to a predetermined pilot pattern, and insert the pilot frequency through subcarrier resources Each MIMO processing result of the subsequent normal data packet and each MIMO processing result of the enhanced data packet after the pilot is inserted are sent out.

Wherein, the second predetermined length limitation is related to the number of antennas of the OFDM system. According to the instructions of the control signaling, the multiple-input multiple-output processing unit performs multiple input on each coding and modulation result of the recombined ordinary data packet and each coding and modulation result of the recombined enhanced data packet in one or more of the following ways Multiple output processing: space-time coding mode, precoding mode, beamforming mode. Wherein, the lengths of the segmentation results of the normal data packet are equal, and the lengths of the segmentation results of the enhanced data packet are equal.

The specific workflow of the launch structure shown in Figure 3 is as follows:

Step 1: The code layer mapping unit further refines the transport block segmentation. Because the principle of the previous transmission block segmentation is to prevent the transmission block from being too large, resulting in excessive memory and complexity of the receiver, so after using the code layer mapping unit, first divide a transmission block (MAC) into a normal data packet and an enhanced data packet . Among them, the ordinary data packet adopts the segmentation principle of the conventional data packet, that is, if the longest limit of the encoded packet is exceeded, the packet will be divided to form the smallest encoding unit; and the enhanced data packet will adopt the multi-antenna technology and fast feedback in the future. mechanism, so the division principle of its data packet no longer adopts the conventional allocation principle, and the maximum length of its packet is limited by the multi-antenna technology adopted. If two-stream multiplexing is used, the maximum length of its packet is twice that of a normal packet , split into encoded packets of two antenna streams. The same encoding and modulation rate and the same control signaling are used to reduce the overhead of control signaling. At the same time, feedback can be selected from a data set (all pairs, pair one, pair two, and all errors). Other performances supporting more antennas can be expanded on this basis.

Step 2: the encoding and modulation module generates modulation symbols. The function completed by this module is forward error correction (FEC for short), which in turn includes a cyclic redundancy check (CRC) unit, a data scrambling unit, a channel coding unit, a rate matching unit, a data interleaving unit, and a modulation processing unit. in:

The CRC check unit is used to calculate the CRC check bits of each transport block. The parity bits are generated from a cyclic generator polynomial and are used to verify the correctness of the received transport block.

The data scrambling unit realizes information scrambling through scrambling, and prevents continuous "0" or "1" from appearing in input bits.

The channel coding unit (such as Turbo code, low density parity check code (low density parity check, LDPC for short), etc.), according to the different coding rates required by the system, achieves the maximum error correction capability through different encoders.

The data interleaving unit interleaves the data through methods such as bit input matrix, intra-row permutation and inter-row permutation of the matrix to ensure that adjacent codes are mapped to different subcarriers to improve frequency diversity gain and performance.

The modulation processing unit maps bit data into complex symbols, such as (QPSK, 16QAM, 64QAM, etc.).

Step 3: The stream mapping unit reassembles the encoding layer to adapt to the structure and hierarchical relationship of the MIMO processing unit.

Step 4: The MIMO processing unit selects the MIMO mode and the combined mode according to the instruction of the control signaling. Among them, the MIMO mode is space-time coding, precoding, beamforming, etc., and the multi-stream packet can select different antenna modes; the combination mode can recombine different antenna modes to maximize system performance.

Step 5: The resource mapping unit performs functions such as subcarrier mapping and pilot insertion. The pilot is inserted according to a certain pilot pattern for receiving channel estimation, and then the data is mapped to subcarriers according to the carrier resources allocated by the user.

Step 6: Form OFDM symbols, that is, convert multiple high-rate symbols into parallel low-rate symbols.

In summary, the present invention provides more flexible HARQ support due to the further refinement of the transport block division. Taking 1 transport block as an example, it is divided into TB 1 and TB2 at the physical layer, and coded and modulated to form symbols s1 and s2 respectively mapped to antenna 1 (ANT1) and antenna 2 (ANT2). , the retransmission method of Alamouti decoding can be adopted, namely $\left[\begin{array}{c}-{\mathrm{the\; s}}_2^{*}\\ {\mathrm{the\; s}}_1^{*}\end{array}\right],$ If only one flow is wrong, the correct flow will be discarded, and the wrong flow will be divided into two ways to adopt $\left[\begin{array}{cc}{\mathrm{the\; s}}_{\mathrm{twenty\; one}}& -{\mathrm{the\; s}}_{\mathrm{twenty\; two}}^{*}\\ {\mathrm{the\; s}}_{\mathrm{twenty\; two}}& {\mathrm{the\; s}}_{\mathrm{twenty\; one}}^{*}\end{array}\right],$ use $\left[\begin{array}{c}-{\mathrm{the\; s}}_1^{*}\\ {\mathrm{the\; s}}_1\end{array}\right],$ Or work in multiple ways such as switching between two antennas, only retransmit the wrong stream and make full use of the characteristics of multiple antennas to improve the reliability of the second retransmission.

In addition, since the present invention further refines the division of the transmission block, the complexity of high-level scheduling is reduced, and resources do not need to be reassigned. After the physical layer is directly decoded, the originally allocated resources can be used for retransmission without requiring high-level rescheduling resources, and the feedback speed is improved to meet the low-latency requirement. In addition, since the subdivided data blocks are modulated with the same code, occupy the same length, occupy the same time-frequency resources, and only require the same control signaling, it has two streams compared to the two-stream design (such as LTE). Feature overhead is doubled again.

In addition, the code layer mapping unit supports one-to-multi-stream input. If the input is a single transport block, the system degenerates to the 16e structure without any changes in the code layer mapping unit. If the input is multiple transport blocks, no changes are made in the code layer mapping unit, and it degenerates to the design of LTE.

The above description is only an embodiment of the present invention, and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of the claims of the present invention.

Claims (6)

1. an emitter that is used for ofdm system is characterized in that, comprising:

Sign indicating number layer map unit, be used to receive transmission block from media access control layer, described transmission block is divided into the general data bag and strengthens packet, and described general data bag is cut apart a plurality of segmentation results that generate described general data bag according to first predetermined length restriction, limit according to second predetermined length described enhancing packet is cut apart a plurality of segmentation results that generate described enhancing packet;

The coded modulation unit, be used for respectively each segmentation result of described general data bag and each segmentation result of described enhancing packet being carried out the coded modulation processing, generate each coded modulation result of described general data bag and each coded modulation result of described enhancing packet;

The stream map unit is used for the structure according to the multiple-input and multiple-output processing unit, and each coded modulation result of described general data bag and each coded modulation result of described enhancing packet are recombinated;

Described multiple-input and multiple-output processing unit, be used for each coded modulation result of the described general data bag after the reorganization and each coded modulation result of the described enhancing packet after the reorganization are carried out the multiple-input and multiple-output processing, generate each multiple-input and multiple-output result of described general data bag and each multiple-input and multiple-output result of described enhancing packet;

The resource map unit, be used for each multiple-input and multiple-output result of described general data bag and each multiple-input and multiple-output result of described enhancing packet being mapped to each subcarrier according to the resource allocation principle, according to predetermined pilot tone pattern the pilot tone pattern is mapped on each subcarrier, and by carrying out contrary fast fourier transform formation OFDM symbol, after inserting Cyclic Prefix, launch by antenna element.

2. emitter according to claim 1 is characterized in that, described second predetermined length restriction is relevant with the number of antennas and the antenna mode of described ofdm system.

3. emitter according to claim 2, it is characterized in that, described multiple-input and multiple-output processing unit is according to the indication of control signaling, one or more mode combinations in the following manner, each coded modulation result of the described general data bag after the reorganization and each coded modulation result of the described enhancing packet after the reorganization are carried out the multiple-input and multiple-output processing: Space Time Coding pattern, precoding pattern, wave beam form pattern.

4. according to each described emitter in the claim 1 to 3, it is characterized in that the equal in length of each segmentation result of described general data bag, the equal in length of each segmentation result of described enhancing packet.

5. emitter according to claim 4 is characterized in that, described coded modulation unit comprises:

The transmission block verification unit is used for the correctness of the described transmission block of verification;

The bit scramble unit is used for each segmentation result of described general data bag and each segmentation result of described enhancing packet are carried out the scrambling processing, generates each scrambling result of described general data bag and each scrambling result of described enhancing packet;

The chnnel coding unit is used for each scrambling result of described general data bag and each scrambling result of described enhancing packet are carried out encoding process, generates the encoding process result of described general data bag and each encoding process result of described enhancing packet;

The data interlacing unit, be used for the encoding process result of described general data bag and each encoding process result of described enhancing packet are carried out the data interlacing processing, generate each interleaving treatment result of described general data bag and each interleaving treatment result of described enhancing packet; And

The modulation treatment unit is used for each interleaving treatment result of described general data bag and each interleaving treatment result of described enhancing packet are mapped as corresponding complex symbol.

6. emitter according to claim 5 is characterized in that, described transmission block verification unit adopts the mode of cyclic redundancy check (CRC) that described transmission block is carried out verification.

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