RU2481714C2 - Hybrid automatic repeat request processing in radio communication systems - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: mobile station can implement uplink channel acknowledgement for hybrid automatic repeat request using frequency hopping to randomise interference between cells. The mobile station can use time multiplexing, frequency multiplexing and/or code multiplexing.

EFFECT: reduced error probability saturation with high speed of movement of mobile stations.

27 cl, 7 dwg

Description

FIELD OF THE INVENTION

The invention relates, in General, to the field of radio communications, in particular to the use of hybrid automatic retransmission request (HARQ) in radio communication systems.

State of the art

To reduce the number of errors in the communication process between base stations and mobile stations in radio networks, the mobile station transmits a response to the signals it receives to indicate whether there were errors in the received signals or not. The communication channel from the base station to the mobile station, referred to as a downlink, may contain packets of a hybrid automatic retransmission request (HARQ request). The channel from the mobile station to the base station, referred to as the uplink, transmits either a positive acknowledgment signal (ACK) or a negative acknowledgment signal (NAK) if errors are present in the transmission.

In principle, in a HARQ system, bits of information are added to the data to be transmitted to detect errors. Based on these bits, the mobile station can determine whether the information transmitted by the base station has been correctly received. It transmits a positive acknowledgment signal if the information was received correctly, or a negative acknowledgment signal otherwise.

The HARQ region is constructed using three mini-tiles with distributed feedback (FMT), each of which has two subcarriers for six characters with orthogonal frequency division multiplexing (OFDM). A method based on code compression was proposed, but it turned out that an approach based on a “clean” code compression can lead to a probability saturation effect (a certain minimum level of probability of error (error floor)) for scenarios with a high degree of mobility, especially in the case of parallel transmissions of several users. A method based on the principles of temporal multiplexing / frequency multiplexing has also been proposed. In time division multiplexing / frequency division multiplexing systems, one HARQ feedback region is divided into six orthogonal feedback channels of the HARQ system using time or frequency division multiplexing. Each HARQ system feedback channel includes three sections having one subcarrier per two OFDM symbols. An orthogonal sequence of two elements can be used to transmit single-bit information of positive acknowledgment or negative acknowledgment. Such an approach using time division / frequency division can overcome the problems of saturation of the probability of errors in high-mobility scenarios. Moreover, the system works stably at various speeds of movement of mobile stations.

The hybrid method with time division multiplexing, frequency division multiplexing, and code division multiplexing is capable of achieving similar characteristics and is also stable in situations with high mobility. However, the main disadvantage of temporary compression / frequency multiplexing systems is that the power of distributed gears in the original design is concentrated in three “tiles”, which can interfere with other cells.

Brief Description of the Drawings

Figure 1 is a schematic description of a first embodiment;

figure 2 represents the structure of the temporal multiplexing / frequency multiplexing of the feedback channel in the HARQ system in accordance with the first embodiment;

figure 3 represents the structure of the temporal multiplexing / frequency multiplexing of the feedback channel in the HARQ system in accordance with another embodiment;

FIG. 4 represents a time division multiplexing / frequency division structure of a feedback channel in a HARQ system in accordance with yet another embodiment; FIG.

5 is a logic diagram of randomization interference in accordance with the first embodiment;

6 is a channel subcarrier indexing diagram in a HARQ system in accordance with a first embodiment;

Fig.7 is a description of an example network of 19 cells, where each cell has three sectors α, β and λ.

DETAILED DESCRIPTION OF THE INVENTION

1, base station 10 can transmit packets capable of HARQ requests through downlink 16 for mobile station 12. Mobile station 12 can create uplink acknowledgment channel 14 for transmitting positive acknowledgment (ACK) or negative acknowledgment (NAK) signals.

Mobile station 12 may include a radio 18 coupled to an OFDM demodulator 20. This OFDM demodulator may be coupled to a symbol demodulator 22 that can perform subcarrier demapping. A symbol demodulator 22 may be coupled to the HARQ system buffer 30. It can also be connected to decoder 24. Error detector 26 determines whether there are errors in the downstream 16 packets allowing HARQ requests and communicates with the HARQ system buffer 30 to indicate the results of the check, as well as with the controller 28.

On the transmitting side, the controller 28 communicates with the encoder 32, as well as with the buffer 30 of the HARQ system. The encoder 32 is connected to a symbol modulator 34, which also maps to subcarriers. This symbol modulator is connected to an OFDM modulator 36, which in turn is connected to a radio transmitter 38.

In accordance with some embodiments of the present invention, inter-cell interference is randomized to ensure stable operation in multi-cell scenarios, as shown in FIG. Interference can be randomized at several levels. The first level (Fig. 5, block 40) can be a permutation in the HARQ region, where the “tiles” of different sectors can be rearranged to other physical time-frequency positions. These permutations are specific for each cell and can be associated with spasmodic rearrangements over time in order to avoid constant conflicts.

Since the time division multiplexing (TBM) / frequency division multiplexing (FDM) method or time division multiplexing / frequency division multiplexing / code division multiplexing (CDM) method is applicable to the HARQ system uplink feedback area, the second level may be inside this HARQ uplink feedback area -systems (Fig. 5, block 42). This may include varying the display of the acknowledgment channel of the HARQ system, indexing the acknowledgment channel of the HARQ system (FIG. 5, block 44) and the sequence of the acknowledgment channel of the HARQ system (FIG. 5, block 46).

Permutation of the control channel (figure 5, block 40) can be implemented as follows. As shown in FIGS. 2 and 3, each acknowledgment HARQ ACK channel includes three HARQ sections. Each such HARQ section contains one subcarrier with two OFDM symbols. There are two ways to map one HARQ section to physical subcarriers, as described in FIGS. 2 and 3.

Permutation channel HARQ ACK acknowledgment can be summarized as follows. First, subcarriers of one HARQ channel are indexed, as shown in FIG. 6. 36 subcarriers of one HARQ channel are indexed according to the scheme P _i , 0≤i <36, where i is the subcarrier index. P _i can be represented as P _{12m + 2l + k} , 0≤m <3.0≤l <6.0≤k <2, where m is the FMT tile index, l is the OFDM symbol index and k is the index subcarrier of one OFDM symbol of one of the 2 × 6 “tiles” of the FMT.

0≤j<36, где j - индекс секции,

- позиция s-й поднесущей в секции j. Первые 18 секций являются секциями Типа 1, а позиции поднесущих могут быть записаны в виде уравнения (1):The entire set of 36 subcarriers can be further divided into 18 sections, each of which has 1 subcarrier into 2 adjacent OFDM symbols. There are two types of sections, as shown in FIGS. 2 and 3, respectively. The section shown in FIG. 2 will hereinafter be referred to as the Type 1 section. The section shown in FIG. 3 will hereinafter be called the Type 2 section. There are 36 positions in total for these two types of sections. The position of one section can be described by the positions of two subcarriers.

0≤j <36, where j is the section index,

is the position of the sth subcarrier in section j. The first 18 sections are Type 1 sections, and the positions of the subcarriers can be written as equation (1):

The remaining 18 sections are Type 2 sections, and the subcarrier positions can be written as equation (2) below:

Subcarrier positions for 6 HARQ ASK acknowledgment channels can be described using 3 sections

, где

.

where

.

In total there are 64 positions for the 0th channel HARQ ACK acknowledgment, which can be determined by the equation below:

и вторую половину R₀ как

. Позиции остальных каналов HARQ ACK квитирования зависят от позиций первого HARQ ACK канала квитирования:Denote the first half of R ₀ as

and the second half of R ₀ as

. The positions of the remaining acknowledgment HARQ ACK channels depend on the positions of the first acknowledgment HARQ ACK channel:

, позиции второго и четвертого каналов HARQ ACK квитирования могут быть описаны двумя уравнения ниже:If

, the positions of the second and fourth channels of the HARQ ACK acknowledgment can be described by the two equations below:

, позиции второго и четвертого каналов HARQ ACK квитирования могут быть описаны двумя уравнения ниже:Otherwise, if

, the positions of the second and fourth channels of the HARQ ACK acknowledgment can be described by the two equations below:

The positions of the three odd HARQ ACK acknowledgment channels can be inferred from the positions of the three even HARQ ACK acknowledgment channels:

where j _{2u + 1, m} = [j _{2u, m} / 2] × 4 + 1-j _{2u, m} , 0≤u <3.0≤m <3.

Thus, in total, for one type of section, there are 65536 types of HARQ ACK channel permutation schemes in one HARQ ACK acknowledgment channel. One permutation scheme in the HARQ ACK acknowledgment channel can be uniquely represented by one index S, where 0≤S <2 ¹⁶ . Such an index S can be represented in binary form a ₀ , a ₁ , a ₂ , ..., a ₁₅ . The first bit a ₀ is the subset selection bit.

If a ₀ = 0

,

,

,

,

otherwise

,

,

,

,

end.

или

, например R₀=(Q₀,Q₈,Q₁₆) или R₀=(Q₀,Q₁₄,Q₁₀). Если индекс схемы перестановок a ₁, a ₂, …, a ₅='00001', эту схему перестановок выбирают посредством второй комбинации из

или

, например R₀=(Q₀,Q₈,Q₁₇) иди R₀=(Q₀,Q₁₄,Q₁₁). Аналогично, биты a ₆, a ₇, …, a ₁₀ и a ₁₁, a ₁₂, …, a ₁₅ используют для описания позиций в каналах HARQ ACK квитирования с номерами 2 и 4, соответственно.The following 5 bits a ₁ , a ₂ , ..., a ₅ can be used to describe positions in the HARQ ACK acknowledgment channel with the designation O. When the index of the permutation scheme is a ₁ , a ₂ , ..., a ₅ = '00000', this permutation scheme selected by the first combination of

or

e.g. R ₀ = (Q ₀ , Q ₈ , Q ₁₆ ) or R ₀ = (Q ₀ , Q ₁₄ , Q ₁₀ ). If the index of the permutation scheme a ₁ , a ₂ , ..., a ₅ = '00001', this permutation scheme is selected by the second combination of

or

For example, R ₀ = (Q ₀ , Q ₈ , Q ₁₇ ) or go R ₀ = (Q ₀ , Q ₁₄ , Q ₁₁ ). Similarly, bits a ₆ , a ₇ , ..., a ₁₀ and a ₁₁ , a ₁₂ , ..., a ₁₅ are used to describe the positions in the HARQ ACK acknowledgment channels with numbers 2 and 4, respectively.

For this section, the index S may change over time, and changing patterns for different sectors may vary, which will maximize the degree of randomization of interference. In one example, the changing pattern for S is a pseudo-random number with a sector-specific random number state. Alternatively, you can plan the S index between sectors. Index S scheduling can be accomplished by scheduling 16 bits of the HARQ channel permutation scheme. One example of such planning uses the network example shown in FIG. 7. The network contains 19 cells with index c and cell identifier (CID), where 1≤cid≤19. Each cell has three sectors α, β, and γ. Sectors can be indexed globally as follows:

a ₀ = sidmod2

a ₁ , a ₂ , ..., a ₅ can be planned in accordance with the table:

[23 30 7 20 24 14 26 29 25 1 28 21 15 18 9 6 3 27 2 10 13 31 5 11 22 8 4 19 17 12 16 0], and the reuse distance is 32. For this sector, a ₁ , a ₂ , ..., a ₅ represent the sidmod32 index in the above table.

a ₆ , a ₇ , ..., a ₁₀ and a ₁₁ , a ₁₂ , ..., a ₁₅ can be planned accordingly.

For a situation with a combination of TDM / FDM / CDM densities, there is one way to map one HARQ section to physical subcarriers, as shown in FIG. 4. Using the TDM / FDM / CDM method, all 36 subcarriers can be further divided into 9 sections, each of which has two subcarriers into two adjacent OFDM symbols. The position of one section can be described by the positions of four subcarriers.

0≤j<9, где j - индекс секции,

, 0≤s<4 - позиция s-й поднесущей секции j. Здесь секции только одного типа, как показано на фиг.4. Позиция поднесущих секции TDM/FDM/CDM может быть описана уравнением (10), приведенным ниже:

0≤j <9, where j is the section index,

, 0≤s <4 - position of the s-th subcarrier section j. Here, sections are of only one type, as shown in FIG. The position of the subcarriers of the TDM / FDM / CDM section can be described by equation (10) below:

There are only two section indices for the first two HARQ ACK acknowledgment channels, so these indices can be defined by the equation below:

If R ₀ = (Q ₀ , Q ₄ , Q ₈ ) the positions of the remaining four HARQ ACK acknowledgment channels can be determined by the two equations below:

If R ₀ = (Q ₀ , Q ₇ , Q ₅ ), the positions of the other four acknowledgment HARQ ACK channels can be described by the two equations below:

Thus, in general, for sections of the same type, there are two types of permutation schemes in the HARQ ACK acknowledgment channel for one such HARQ ACK acknowledgment channel. One bit is enough to describe permutations in the acknowledgment ACK channel.

The permutation of indices in the HARQ subchannel (Fig. 5, block 44) can be performed as follows. When one acknowledgment HARQ ACK channel is assigned to one mobile station, it is assigned with a logical HARQ acknowledgment ACK channel index. We denote the logical index of the acknowledgment channel ACK by k, so that the range of this index k can be determined by the group of logical indices of the acknowledgment channel ACK of a particular subframe. The nature of the mapping of the logical index of the HARQ channel ACK acknowledgment to the physical index of the channel HARQ ACK acknowledgment may change over time, and the pattern of change depends on the particular cell. For one acknowledgment ACK area, 720 channel index permutations take place. For each permutation of the channel indices, the mapping of the logical index of the acknowledgment ACK channel to the physical index of the acknowledgment ACK channel is different from the others. In one example, in each sector, the permutation scheme is changed in accordance with a pseudo-random number from 0 to 719. The state of a random number in each sector is also different from the others.

Alternatively, a channel index may be planned if there is enough information to coordinate between sectors. Using the example in Fig. 7, we can write the law of permutation of the channels in the form of the function below:

This equation assumes that when assigning a logical index to the acknowledgment ACK channel, each base station will assign such indices from the lowest available logical index of the acknowledgment ACK channel or from the largest available logical index of the acknowledgment ACK channel. Then, in the case of a small load, interference between the ACK channels between the cells can be orthogonal during the frequency domain.

The permutation of the HARQ sequence (figure 5, block 46) is as follows. The sequence used to transmit a positive acknowledgment (ACK) or negative acknowledgment (NAK) signal in the physical HARQ channel of the acknowledgment ACK can be defined as [1, e ^jθ ] for positive acknowledgment (ACK) and [1, -e ^jθ ] for negative Acknowledgment (NAK), where θ may vary with time and section, and the pattern of change depends on a particular cell. One example is θ∈ {0, π / 4, π / 2,3π / 4, π, 5π / 4,3π / 2,7π / 4}, where the phase index is a pseudo-random number and the state depends on the sector. Planning is also possible when there is enough information to coordinate between sectors. Using the network example shown in FIG. 7, the phase index can be determined according to the equation below:

In some embodiments, the sequence shown in FIG. 5 may be implemented in software, hardware, software, or hardware. In the hardware version, this can be implemented by the HARQ module 30 shown in FIG. In a software embodiment, this can be implemented by computer-readable instructions then executed by a computer, such as a controller 28, and recorded on a suitable recording medium, such as magnetic, optical, or semiconductor memory. This memory may be part of the HARQ module 30 shown in FIG. 1, or the controller 28 as two examples.

In some embodiments, radios designated herein as a base station and a mobile station may have one or more antennas. In one embodiment, both the mobile station and the base station may have one transmit antenna and two receive antennas.

References in the present description to “one option”, “first option” or “some option” mean that a particular feature, structure or characteristic described here in connection with the considered option is included in at least one implementation example covered by the present invention. Thus, the appearance of the phrase “one option” or “some option” does not necessarily refer to the same option. Moreover, a particular feature, structure or characteristic may be embodied in a different suitable form than that of the specific embodiment discussed here, and all such forms may be embraced by the claims of the present invention.

Although the present invention has been considered here for a limited number of options, specialists can offer numerous modifications and deviations from these options. The appended claims cover all such modifications and changes that fall within the spirit and scope of the present invention.

Claims (27)

1. A transmission method comprising:
the use of frequency hopping for radiocommunication randomization of inter-cell interference for an acknowledgment channel in a system with a hybrid automatic retransmission request using frequency hopping; and the use of temporary or frequency multiplexing for radio communications, characterized in that the frequency hopping includes the use of permutation in the control channel. 2. The method according to claim 1, including the use of frequency hopping in the acknowledgment channel using also code multiplexing. 3. The method according to claim 1, further comprising using permutations of the subchannel with a hybrid automatic request for retransmission. 4. The method according to claim 3, further comprising using permutations of the subchannel indices with a hybrid automatic retransmission request. 5. The method according to claim 4, further comprising rearranging the "tiles" of various sectors to other physical time-frequency positions. 6. The method according to claim 1, including the use of a channel with a hybrid automatic request for retransmission, which includes three sections of a channel with a hybrid automatic request for retransmission, each section includes one subcarrier with two symbols with orthogonal frequency division multiplexing. 7. The method according to claim 6, comprising displaying one section with a hybrid automatic request for retransmission to physical subcarriers. 8. The method according to claim 1, including the representation of channel permutation schemes with a hybrid automatic request for retransmission by means of a single index S, where this index S is not less than zero and not more than 2 ¹⁶ . 9. The method of claim 8, including allowing the index S to change over time, so that the patterns of changes in different sectors may vary to maximize randomization of interference. 10. The method of claim 8, including scheduling an index S between sectors. 11. A machine-readable recording medium that stores instructions that allow a computer to:
use frequency hopping for radio communications, randomize inter-cell interference for an acknowledgment channel in a system with a hybrid automatic retransmission request using frequency hopping;
use a temporary or frequency seal for radio communications; and use permutations in the control channel. 12. The medium of claim 11, further storing instructions for using frequency hopping in the acknowledgment channel also using code multiplexing. 13. The medium of claim 11, further storing instructions for using permutations of a subchannel with a hybrid automatic retransmission request. 14. The medium of claim 13, further storing instructions for using permutations of the subchannel indices with a hybrid automatic retransmission request. 15. The medium of claim 14, further storing instructions for rearranging tiles of various sectors to other physical time-frequency positions. 16. The medium of claim 11, further storing instructions for using a hybrid automatic retransmission request channel, which includes three channel sections with a hybrid automatic retransmission request, each section including one two-symbol subcarrier with orthogonal frequency division multiplexing. 17. The medium of claim 16, further storing instructions for displaying one section with a hybrid automatic request for retransmission to physical subcarriers. 18. A mobile station comprising:
a unit for using frequency hopping to randomize inter-cell interference for an acknowledgment channel with a hybrid automatic retransmission request using time or frequency multiplexing;
a receiver connected to said unit; and
a transmitter connected to the specified unit, in which the specified unit uses frequency hopping with permutations in the control channel. 19. The mobile station of claim 18, wherein said block is an acknowledgment buffer for automatically requesting a retransmission. 20. The mobile station according to claim 18, wherein said block is a controller. 21. The mobile station of claim 19, comprising an automatic retransmission request buffer connected to a character modulator and to an encoder on the side of the radio transmitter and to a character demodulator and to an error checking unit on the side of the radio receiver. 22. The mobile station of claim 18, wherein the mobile station uses code division multiplexing. 23. The mobile station of claim 18, wherein said block uses subchannel permutations with a hybrid automatic retransmission request. 24. The mobile station of claim 23, wherein said block uses permutation of the subchannel indices with a hybrid automatic retransmission request. 25. The mobile station according to paragraph 24, where the specified block rearranges the "tiles" of various sectors in other physical frequency-time positions. 26. The mobile station of claim 18, wherein said block uses a hybrid automatic retransmission request channel, which includes three sections of a hybrid automatic retransmission request channel, each section including one subcarrier with two signals with orthogonal frequency division multiplexing. 27. The mobile station according to claim 26, wherein said block displays one section with a hybrid automatic request for retransmission to a physical subcarrier.

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