KR20080016541A - Communication system and method - Google Patents

Abstract

In a system like CDMA, SC, OFDM, OFDMA, etc., a new method is disclosed for computing and using the parameter d for all blocks. The Bit Interleaver uses a constant parameter (named "d", and it equals for example 16 in 802.16), in order to perform its inner permutations. Improved performance is achieved by manipulating the "d" parameter of the formula per modulation and encoded block, using data from a table. An example applicable with the current 802.16d (2004) for the "d" parameter is also disclosed.

Description

Communication system and method

The present invention relates to a communication system and method, and more particularly to a system and method using FEC blocks.

The OFDM PHY, defined as an example within the IEEE 802.16d / e standard and the DVB-RCT standard, uses a two-dimensional allocation method (in frequency and time domain) to allocate slots for transmission.

An example of a possible transmission frame is shown in FIG. 1, where different bursts in the DL are of different shades. The same method is used for UL.

Each burst may contain several FEC blocks; FEC blocks are the basic entities of an encoding chain and are processed within that encoding chain.

In the definition of OFDMA, an encoding chain using a convolutional encoder is a byte level or / and symbol level or / and bit as one example of a bit interleaver or DVB-T as one of the chain processing elements. Use an interleaver that requires some other FEC encoding that may appear in the level.

Bit interleaver definitions are given in the standard and follow the following definitions, for example 802.16d OFDMA:

All encoded data bits shall be interleaved by a block interleaver with a block size according to the number of encoded bits per encoded block size N _cbps as set in _8.4.9.2 . Interleaver is defined by two stages of substitution. The first allows adjacent coded bits to be mapped to non-adjacent subcarriers. The second substitution allows adjacent coded bits to be alternately mapped to higher or lower order bits than the most significant bits of the array, thereby avoiding long-running bits.

N _cbps is referred to as the number of encoded bits per carrier. That is, 2, 4, or 6 for QPSK, 16-QAM or 64-QAM, respectively. s = N _cbps / 2. In a block of N _cbps bits at the time of transmission, k is an indicator of the encoded bit before the first substitution, m _k is an indicator of the encoded bit after the first substitution and before the second substitution, and j _k is modulation mapping. The index after the second substitution just before is called d and modulo is used for the substitution.

The first substitution is defined by the formula:

m _k = (N _cbps / d) ^. k _{mod (d)} + f _loor (k / d)

k = 0, 1, ..., N _cbps -1, d = 16

The second substitution is defined by the equation

j _k = s ^. f _loor (m _k / s) + (m _k + N _cbps -f _loor (d ^. m _k / N _cbps )) _{mod (s)}

k = 0, 1, ..., N _cbps -1, d = 16

A de-interleaver that performs the inverse operation of the interleaver is also defined by two substitutions.

Within a block of received N _cbps bits, j is an indicator of the received bit before the first substitution, m _j is an indicator of the bit after the first substitution and before the second substitution, and k _j is the block to the decoder. This is called the index after the second substitution just before delivery.

The first substitution is defined by the formula:

m _j = s ^. f _loor (j / s) + (j + f _loor (d ^. j / N _{cbps)) mod (s)}

j = 0, 1, ..., N _cbps -1, d = 16

The second substitution is defined by the equation

j _k = d ^. m _j -(N _cbps -1) ^. f _loor (d ^. m _j / N _cbps )

j = 0, 1, ..., N _cbps -1, d = 16

The first substitution in the deinterleaver is the inverse of the second substitution in the interleaver and vice versa.

Various terms are used in the disclosure of the present invention, FEC, OFDMA PHY, DVB-RCT ETSI, PUSC, FUSC, OFUSC, AMC are well known in the art and defined in various standards such as IEEE 802.16d / e standard. will be.

In systems such as CDMA, SC, OFDM, OFDMS, etc., in order to perform internal substitution, parameter d is used for all blocks and bit interleaver is used as a constant parameter. Same thing).

Combining this interleaver with OFDMA substitution in other modes, such as PUSC, FUSC, OFUSC, AMC (they use different methods for scattering and / or grouping of subcarriers of time or / and frequency in the transmitted frame) It is possible to improve the result at a very small minimum distance between the interleaved bits.

The solution to this problem is given by processing the "d" parameter of the formula for the modulated and encoded blocks. The following tables show examples that apply to the current 802.16d (2004) for the "d" parameter. This optimization results in high precision minimum-distance between interleaved bits and improved performance of the link. For example, improved performance against interference may be obtained.

Other objects, benefits and other features of the present invention will become apparent to those skilled in the art from the disclosure set forth below.

1 to 4 show examples of possible transmission frames.

5-7 are tabular and show details of the data used in the preferred embodiment of the present invention.

8 to 10 show in detail how to implement the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described by way of example and with reference to the accompanying drawings.

1 and 2 show examples of possible transmission frames. Different bursts in the DL are shown in different shades or enclosed within a square within it.

Two-dimensional transmissions are enumerated in the time / frequency space, with the frequency axis 11 representing a subchannel, the time axis comprising downlink (DL) 12 and uplink (UL) 13 steps. The frame includes a preamble 21, DL and UL map 22 bursts 23, 24, 25, 26, 27, 28.

Table 1 of Figure 5 shows examples of implementations of the invention, where parameter d is derived as a result of processing the "d" parameter of the formula for the modulated and encoded block.

The table shows an example applied to the current 802.16d (2004) for parameter "d", which optimization results in high precision minimum-distance between interleaved bits and improved performance of the link.

This further optimization of the FEC block can improve the system in situations where burst errors are encountered with portions of the FEC block, which may be due to the speed or other reasons of other cells, sector interferers or mobiles. It can be generated by each or a combination of frequency / time fading that can produce frequency selective fading (holes) that move to the time zone related to the Doppler effect caused.

This multi-parameter d or any scattered spreading parameter can be optimized symbol, byte and bit interleaver for other FEC methods such as, for example, block code RS, TPC, LDPC, or convolutional codes such as CC, CTC, etc. It can be applied at other levels for example.

The above improvement in the present invention can be concluded with a closed loop method: a parameter that is scattered by a moving or fixed user is scattered by interference randomly encountering a sequence of adjacent bits of the block code that reduces the capacity of the code. If it detects that it is not suitable as a location facing the subcarrier, the mobile terminal which detects such a situation can request the base station to change a parameter to break this sequence.

Of course, any repetitive code, ARQ code or HARQ can change the scattered parameters by selecting a different set of scattered parameters for each transmission, which will effectively give the divers seat the desired result of frequency hopping and time hopping. .

Interweaver in Multiple Burst Transmissions

The OFDMA PHY defines: For example, the IEEE802.16d / e standard and the DVB-RCT ETSI standard use a two-dimensional allocation method (in frequency and time domain) to allocate slots for transmission, An example can be seen in FIGS. 3 and 4.

Two-dimensional transmissions are enumerated in the time / frequency space, with the frequency axis 11 representing a subchannel, the time axis comprising downlink (DL) 12 and uplink (UL) 13 steps. The frame includes a preamble 21, DL and UL map 22 bursts 23, 24, 25, 26, 27, 28.

Different bursts in the DL are shown in different shades, and the same method is used in the UL.

Each burst may contain several FEC blocks; FEC blocks are the basic entities of an encoding chain and are processed within that encoding chain.

In the definition of OFDMA, an encoding chain using a convolutional encoder is a byte level or / and symbol level or / and bit as one example of a bit interleaver or DVB-T as one of the chain processing elements. Use an interleaver that requires some other FEC encoding that may appear in the level.

Bit interleaver definitions are given in the standard and follow, for example, the definition of 802.16d OFDMA described above:

The present invention may be used in systems such as CDMA, SC, OFDM, OFDMS, and the like. There may be various variations on the parameter d used for all blocks to carry out the substitutions therein, and the bit interleaver uses one or more constant parameters ("d" means for example 16 and 16 in 802.16). Same thing).

Combining OFDMA substitution in this interleaver with other modes (PUSC, FUSC, OFUSC, AMC-they use a different method for scattering and / or grouping of subcarriers of time or / and frequency in the transmitted frame) is interleaved It is possible to improve the result at a very small minimum distance between the bits being.

The present invention implements this new innovative concept by processing the "d" parameter of the formula for the modulated and encoded block. The following tables provide examples that apply to the current 802.16d (2004) for the "d" parameter. Shows.

This optimization results in high precision minimum-distance between the interleaved bits and improved performance of the link (d is calculated as 48 * N when N is the number of slots transmitted). See Table 2 in FIG. 6.

Other methods of optimizing the parameter d may be used.

For example, another implementation of optimizing d may use the following formula.

d = 12 * N or

d = 6 * N

However, other methods may optimize each transmission type using its own unique parameters to obtain optimal performance for each transmission type (depending on the mode, modulation and number of slots used).

This further optimization of the FEC block can improve the system in situations where burst errors are encountered with portions of the FEC block, which may be due to the speed or other reasons of other cells, sector interferers or mobiles. It can be generated by each or a combination of frequency / time fading that can produce frequency selective fading (holes) that move to the time zone related to the Doppler effect caused.

This multi-parameter d or any scattered spreading parameter can be optimized symbol, byte and bit interleaver for other FEC methods such as, for example, block code RS, TPC, LDPC, or convolutional codes such as CC, CTC, etc. It can be applied at other levels for example.

How to optimize your transfer

This method includes the following steps (see FIG. 8).

(a) receiving the type, modulation and number of slots used for each transmission type;

(b) setting unique parameters to obtain optimal performance for each transmission type;

(c) applying said unique parameters for further optimization per FEC block; And

(d) applying the multi-parameter d or scattered spreading parameters to other levels, such as symbols, bytes and bit interleaves.

Close Loop [CL] Scattering

The above description of the present invention when the moving or fixed user detects that the scattered parameter is not suitable for a location where it encounters a subcarrier scattered by random encounters with a sequence of adjacent bits of the block code that reduces the capacity of the code. The improvement can be a closed loop method. Upon detecting such a situation, the mobile station can request the base station to change a parameter that breaks the sequence, for example, can have two parameters d per FEC block.

Method for Scattering Closed Loop [CL]

This method includes the following steps (see FIG. 9).

(a) Whether or not the scattered parameter is suitable for a location where it encounters a scattered subcarrier by interference randomly encountering a sequence of adjacent bits of the block code that reduces the capacity of the code. By) detecting or measuring;

(b) proceeding to step (a) if the scattered parameters are satisfactory;

(c) requesting a base station for a parameter change (by the mobile terminal) to break the sequence;

(d) if possible (by the base station) answer with a parameter change that will break the sequence; And

(e) proceeding to step (a).

If possible, the base station can answer with a parameter change that will break the sequence. For example, it may have two parameters d per FEC block.

Repeat code and ARQ

Of course, any repetition code, ARQ code or HARQ can change the scattered parameter by selecting a different set of scattered parameters for each transmission, coordinating with ARQ combined with CL scattering, and scattering as part of the ARQ ACK / NACK. The number of parameters gives the result of controlled closed loop frequency hopping and time hopping to two levels of diversity.

Thus, in this way, the bits that can be located in one transmission are located in the appropriate positions in the next transmission and provide a suitable improvement in coordination with combined algorithms such as selection of bits / symbols, MRC, etc. . In the case of simple iteration, several different scattered parameters are preselected to provide an open loop (OL) solution suitable for quickly changing channels or interfaces.

Method for iterative code and ARQ

This method includes the following steps (see FIG. 10).

(a) changing the scattered parameter for the repetition code, ARQ code or HARQ by selecting a different set of scattered parameters for each transmission;

(b) coordinating with ARQ coupled with CL scattering, and the number of scattered parameters as part of the ARQ ACK / NACK provides results of controlled closed loop frequency hopping and time hopping to two levels of diversity;

(c) As a result, the bits that can be located in a hole in one transmission are located in the appropriate positions in the next transmission and provide appropriate improvements in coordination with combined algorithms such as selection of bits / symbols, MRC, etc. Doing; And

(d) in the case of simple iteration, preselecting several different scattered parameters to provide an open loop (OL) solution suitable for quickly changing channels or interfaces.

However, other methods can optimize each transmission type using its own unique parameters to achieve optimal performance for each transmission type (depending on the mode, modulation, and number of slots used).

However, other solutions will be used to optimize each block size for each modulation type shown by the example with reference to Table 3 (FIG. 7).

Various embodiments of the systems and methods listed above, depending on the structure and processing of the systems listed in the present disclosure, may be devised.

The foregoing descriptions are merely examples of apparatuses and methods within the scope of the present invention, and it will be apparent to those of ordinary skill in the art that various modifications will be made to the presently disclosed disclosure. It must be recognized.

Claims (18)

In a communication system having bursts with FEC blocks, for each block, a method using the other available values of parameter d, which is used to perform internal substitution. The method of claim 1, Wherein said communication system is based on CDMA, SC, OFDM, OFDMA, or a combination thereof. The method of claim 1, The parameter d is used for performing internal substitution in a bit interleaver. The method of claim 1, The parameter d is used for performing internal substitution in a bit deinterleaver. The method of claim 1, The parameter d is used for performing internal substitution in bit interleaver and OFDMA substitution of different modes PUSC, OFUSC or AMC. The method of claim 1, The parameter d is calculated as d = 12 * N. The method of claim 1, The parameter d is calculated as d = 6 * N. The method of claim 1, The communication parameters are set as listed in Tables 1, 2 or 3. In a communication system having a burst using FEC blocks, the method for transmission optimization, (a) receiving the type, modulation and number of slots used for each transmission type; (b) setting unique parameters to obtain optimal performance for each transmission type; (c) applying said unique parameters for further optimization per FEC block; And (d) applying the multi-parameter d or scattered spreading parameters to other levels, such as symbols, bytes, and bit interleaves. The method of claim 9, And the parameter is a parameter d used in an interweaver of a multi-burst transmission. The method of claim 9, Wherein said communication parameters are set as listed in Tables 1, 2 or 3. In a communication system having bursts with FEC blocks, a method for closed loop (CL) scattering, the method comprising: (a) whether or not the scattered parameter is suitable for a location where it encounters a scattered subcarrier by interference randomly encountering a sequence of adjacent bits of the block code that reduces the capacity of the code; By) detecting or measuring; (b) proceeding to step (a) if the scattered parameters are satisfactory; (c) requesting a base station for a parameter change (by the mobile terminal) to break the sequence; (d) if possible (by the base station) answer with a parameter change that will break the sequence; And (e) proceeding to step (a). The method of claim 12, The parameter is a parameter d used in the interweaver of the multiple burst transmission. The method of claim 13, Wherein the communication uses two different d parameter values per FEC block. The method of claim 12, The communication parameters are set as listed in Tables 1, 2 or 3. In a communication system having a burst using FEC blocks, the method for repetition code and ARQ, (a) changing the scattered parameter for the repetition code, ARQ code or HARQ by selecting a different set of scattered parameters for each transmission; (b) coordinating with ARQ coupled with CL scattering, and the number of scattered parameters as part of the ARQ ACK / NACK provides results of controlled closed loop frequency hopping and time hopping to two levels of diversity; (c) As a result, the bits that can be located in a hole in one transmission are located in the appropriate positions in the next transmission and provide appropriate improvements in coordination with combined algorithms such as selection of bits / symbols, MRC, etc. Doing; And (d) in the case of simple repetition, preselecting various other scattered parameters to provide an open loop (OL) solution suitable for quickly changing the channel or interface. The method of claim 16, The parameter is a parameter d used in the interweaver of the multiple burst transmission. The method of claim 16, The communication parameters are set as listed in Tables 1, 2 or 3.

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