阅读说明：本技术 支持harq的设备和方法 (Apparatus and method for supporting HARQ ) 是由 希米·西隆 里奥尼德·爱普斯坦 亚龙·本-阿里 埃泽尔·梅尔泽 于 2018-10-22 设计创作，主要内容包括：本发明涉及HARQ,尤其用于IEEE 802.11,即,Wi-Fi的HARQ。本发明提出了一种用于支持该HARQ的发送设备,其中与传统的发送器相比,加扰和编码的顺序被改变。同样,本发明提出了一种用于支持该HARQ的接收设备,其中,与传统接收器相比,解扰和解码的顺序被改变。具体地,发送设备用于使用前向纠错(FEC)编码对至少一个数据单元进行编码,基于加扰种子对编码的数据单元进行加扰,提供从加扰和编码的数据单元中分离出的加扰种子的指示,以及发送加扰种子的指示,然后发送加扰和编码的数据单元到接收设备。(The present invention relates to HARQ, and is particularly useful for HARQ for IEEE 802.11, i.e., Wi-Fi. The present invention proposes a transmission apparatus for supporting the HARQ, in which the order of scrambling and encoding is changed compared to a conventional transmitter. Also, the present invention proposes a receiving apparatus for supporting the HARQ, in which the order of descrambling and decoding is changed compared to a conventional receiver. In particular, the transmitting device is configured to encode at least one data unit using Forward Error Correction (FEC) encoding, scramble the encoded data unit based on a scrambling seed, provide an indication of the scrambling seed separated from the scrambled and encoded data unit, and transmit the indication of the scrambling seed prior to transmitting the scrambled and encoded data unit to the receiving device.)

1. Transmitting device (100) for supporting hybrid automatic repeat request, HARQ, the transmitting device (100) being configured to:

encoding at least one data unit (101) using forward error correction, FEC, encoding (102),

scrambling the encoded data unit (103) based on a scrambling seed (104),

providing an indication (105) of the scrambling seed (104) separated from the scrambled and encoded data unit (106), and

-sending an indication (105) of the scrambling seed (104), and then sending the scrambled and encoded data unit (106) to a receiving device (300).

2. The transmitting device (100) of claim 1, configured to:

encoding and/or modulating an indication (105) of the scrambling seed (104) separated from the at least one data unit (101).

3. The transmitting device (100) according to claim 1 or 2, configured to:

including an indication (105) of the scrambling seed (104) in a physical layer (PHY) preamble.

4. The transmitting device (100) according to any one of claims 1 to 3, configured to:

include an indication (105) of the scrambling seed (104) in a signal A SIG-A field or a signal B SIG-B field.

5. The transmitting device (100) of claim 1, configured to:

defining an indication (105) of the scrambling seed (104) based on predetermined bits of one or more signaling fields.

6. The transmitting device (100) according to any one of claims 1 to 5, configured to:

encoding an indication (105) of the scrambling seed (104) using a binary convolutional code, BCC.

7. The transmitting device (100) according to any one of claims 1 to 6, configured to:

encoding an indication (105) of the scrambling seed (104) using a block code.

8. The transmitting device (100) of claim 7, configured to:

encoding an indication (105) of the scrambling seed (104) using a Hadamard code as a generator matrix (500).

9. Transmitting device (100) according to any of claims 1 to 8, configured to

Modulating an indication (105) of the scrambling seed (104) using binary phase shift keying, BPSK.

10. Receiving device (300) for supporting hybrid automatic repeat request, HARQ, the receiving device (300) being configured to:

receiving an indication (105) of a scrambling seed (104) from a transmitting device (100) and then receiving at least one scrambled and encoded data unit (106) separated from the indication (105) of the scrambling seed (104),

descrambling the scrambled and encoded data unit (106) based on the scrambling seed (104) determined from the indication (105) of the scrambling seed (104), and

the encoded data unit (103) is decoded using forward error correction, FEC, decoding (301).

11. The receiving device (300) of claim 10, configured to:

-sending an acknowledgement, ACK, and/or a negative acknowledgement, NACK, message for at least one correctly and/or incorrectly decoded data unit (101) to the sending device (100),

receiving a further indication (105) of a scrambling seed (104) from the transmitting device (100) if the decoding of at least one of the data units (101) fails, and then receiving a scrambled and encoded retransmission of the failed data unit (101) separated from the further indication (105) of the scrambling seed (104),

descrambling the scrambled and encoded retransmission of the failed data unit (101) based on a scrambling seed (104) determined from a further indication (105) of the scrambling seed (104),

decoding the encoded retransmission of the failed data unit using forward error correction, FEC, decoding (301), an

Soft combining the retransmission of the failed data unit (101) with the previously received failed data unit (101).

12. The receiving device (300) of claim 10 or 11, configured to:

an indication (105) of a received scrambling seed (104) separated from a received scrambled and encoded data unit (106) is decoded and/or demodulated, respectively.

13. The receiving device (300) of any of claims 10 to 12, configured to:

obtaining an indication (105) of a scrambling seed (104) from predetermined bits of one or more signaling fields received by the transmitting device (100).

14. The receiving device (300) of any of claims 10 to 13, configured to:

extracting an indication (105) of a scrambling seed (104) from a physical layer PHY preamble, in particular from a signal A SIG-A field or a signal B SIG-B field, received by the transmitting device (100).

15. A method (200) for supporting hybrid automatic repeat request, HARQ, the method comprising:

encoding (201) at least one data unit (101) using forward error correction, FEC, encoding (102),

scrambling (202) the encoded data unit (103) based on a scrambling seed (104),

providing (203) an indication (105) of the scrambling seed (104) separated from the scrambled and encoded data unit (106), and

-sending (204) an indication (105) of the scrambling seed (104), followed by sending the scrambled and encoded data unit (106).

16. A method (400) for supporting hybrid automatic repeat request, HARQ, the method (400) comprising:

receiving (401) an indication (105) of a scrambling seed (104) and then receiving at least one scrambled and encoded data unit (106) separated from the indication (105) of the scrambling seed (104),

descrambling (402) the scrambled and encoded data unit (106) based on a scrambling seed (104) determined from the indication (105) of the scrambling seed (104), and

the encoded data unit (103) is decoded (403) using forward error correction, FEC, decoding (301).

Technical Field

The present invention relates to Hybrid Automatic Repeat Request (HARQ) in wireless communication technology, and more particularly to HARQ for IEEE 802.11, i.e., HARQ for Wi-Fi. To this end, the present invention proposes a transmitting device and a receiving device for supporting the HARQ in Wi-Fi, respectively, and further proposes a corresponding HARQ method compatible with IEEE 802.11.

Background

HARQ is a widely used method in wireless and cellular technologies, in which past transmissions and current retransmissions are combined to improve decoding performance. All current 802.11 standards (i.e., a/b/g/n/ac/ax) do not support HARQ. In particular, in communication systems according to these standards, the encoded data bits are scrambled at the transmitter side and the scrambling seed used is encoded together with the data payload. This means that at the receiver side, the scrambling seed for scrambling (and hence descrambling required) is only known after decoding, and therefore only the decoded bits can be descrambled. This means that Log Likelihood Ratios (LLRs) at the input of the receiver cannot be descrambled and cannot be combined in the HARQ scheme.

Furthermore, 802.11 communication systems typically use aggregate Media Access Control (MAC) Protocol Data units (a-MPDUs), where multiple MPDUs (i.e., Data units) are aggregated to form a long transmission (thus effectively reducing overhead), i.e., a single Physical Protocol Data Unit (PPDU). Since the physical layer (PHY) runs over the entire PPDU, independent of MPDUs, the scrambling seed is encoded using the first MPDU. If the first MPDU is decoded correctly and at the same time at least one MPDU fails to decode, the transmitter will retransmit the failed MPDU and append an indication of the scrambling seed used to the (now) first MPDU. This means that after encoding, in particular after Forward Error Correction (FEC) encoding, the encoded bits will be different from the previous transmission on the transmitter side, making receiver-side combining practically impossible.

In all current versions of the 802.11 standard (a/b/g/n/ac/ax), the scrambler operates on the information bits (which are provided to the PHY by the MAC layer) at the transmitter end before invoking FEC operation (coding) -it can be either Binary Convolutional encoder (BCC) or Low Density Parity Check Code (LDPC). For example, fig. 7 shows a block diagram of an 802.11n transmitter 700. Fig. 2 shows a block diagram of an 802.11ax transmitter 800. In both transmitters 700 and 800, scramblers 701 and 801 are provided before FEC/BCC encoders 702 and 802.

The scramblers 701 and 801 are used to avoid long sequences of identical repeated bits (0 or 1 s) in the bit stream, so their outputs should be at least pseudo-random. This helps to improve the Peak to Average Power Ratio (PAPR) and also ensures that interfering transmissions from other Stations (STAs), i.e. transmitters 700 and 800, are in the extreme case synchronized, which behaves more like random noise.

The scrambling seeds of the scramblers 701 and 801 are therefore chosen randomly and typically vary between transmissions in order to limit PAPR on average. Each data portion of a PPDU (comprising one or more data units) is typically provided with a 16-bit SERVICE field containing a 7-bit scrambler initialization and 9 zero bits. SERVICE field 900 is shown in fig. 9. The SERVICE field 900 is used as an indication of the scrambling seed.

SERVICE field 900 is then encoded with the data portion. This means that when, for example, using LDPC, only the first LDPC codeword (only) contains the SERVICE field. On the receiver side, immediately after the start of the data decoding process, the first 7 bits of the decoder output (related to scrambler initialization) are used to configure the descrambler.

As described above, for example, in IEEE 802.11, the configurations of scramblers 701 and 801 (including SERVICE field 900) and FEC have the following disadvantages:

scrambling seed information (within SERVICE field 900) is contained in the first MPDU, so any retransmission of an MPDU (which is not the first MPDU) in a new transmission must include SERVICE field 900, thus altering the coded bits.

Since the descrambler is deployed after the FEC decoder (at the receiver side), in order to make it HARQ compatible, the scrambling seed for each transmission/retransmission must be the same to ensure that both the original transmission and the subsequent (optional) retransmission carry (possibly different redundancy versions of) the same codeword.

SERVICE field 900 is encoded and modulated the same as the data payload, which means that even if there is no error anywhere in the actual payload of the PPDU, an error in the decoding scrambling seed will cause the decoding of the entire PPDU to fail

Disclosure of Invention

In view of the above problems and disadvantages, embodiments of the present invention are directed to improving the current embodiments. The aim is to make wireless communication technologies, in particular IEEE 802.11, i.e. Wi-Fi, compatible with HARQ. Therefore, all transmissions/retransmissions should use a (semi-) random scrambling seed (similar to non-HARQ retransmissions). Furthermore, a robustness scheme should be provided to indicate the scrambling seed to the receiving side to protect the scrambling seed to avoid (or at least make less likely to) fail decoding the entire (aggregated) data unit due to errors occurring when decoding the indication of the scrambling seed. The solution of the invention should further be compatible with the present embodiments.

The object of the invention is achieved by the solution presented in the appended independent claims. Advantageous embodiments of the invention are further defined in the dependent claims.

Specifically, the present invention proposes a transmitting apparatus that performs scrambling after FEC encoding, and a receiving apparatus that performs descrambling before FEC decoding. In addition, the scrambling seed indication is separate from the transmitted data unit.

A first aspect of the present invention provides a transmitting apparatus for HARQ, the transmitting apparatus being configured to: the method may further include encoding at least one data unit using the FEC encoding, scrambling the encoded data unit based on a scrambling seed, providing an indication of the scrambling seed separate from the scrambled and encoded data unit, and transmitting the indication of the scrambling seed, and then transmitting the scrambled and encoded data unit to the receiving device.

Thus, unlike the current transmitter implementation, FEC is performed before scrambling, i.e. an FEC encoder may be arranged before the scrambler in the transmitting device. In this way, a combination of multiple transmissions becomes possible with a (e.g., random) scrambling seed that changes with each transmission. Furthermore, by separating the indication of the scrambling seed from the data unit, the indication may be provided to the receiving device in a more robust manner, thereby reducing decoding errors. Separate means that the indication of the scrambling seed is sent separately from the data unit or encoded and/or modulated differently from the data unit.

If scrambling and FEC coding are not switched, it is virtually impossible to descramble the LLRs and combine them for multiple retransmissions at the receiving device. Furthermore, if the indication of the scrambling seed is not separated from the data units (data payload), each retransmission will result in a different set of coded bits, indicating that their LLRs cannot be combined, if the first data unit is different from the previous transmission.

One data unit may be an MPDU. The plurality of data units may be a-MPDUs, i.e., PPDUs.

In one implementation form of the first aspect, the sending device is configured to: encoding and/or modulating an indication of the scrambling seed separated from the at least one data unit.

Thus, the scrambling seed may be encoded and/or modulated in a more robust manner, e.g. in a scheme with stronger encoding or modulation, to reduce the risk of decoding errors. Therefore, the probability of decoding the entire data unit failing is less and fewer retransmissions are required.

In a further implementation form of the first aspect, the sending device is configured to: include an indication of the scrambling seed in a PHY preamble.

In a further implementation form of the first aspect, the sending device is configured to: include an indication of the scrambling seed in a signal A (SIG-A) field or a signal B (SIG-B) field.

In a further implementation form of the first aspect, the sending device is configured to: defining an indication of the scrambling seed based on predetermined bits of one or more signaling fields.

The above form of embodiment is easy, but it is a more efficient option to separate the indication of the scrambling seed from one or more data units.

In a further implementation form of the first aspect, the sending device is configured to: encoding the indication of the scrambling seed using a Binary Convolutional Code (BCC).

Thus, the indication is encoded differently than the data unit, in particular more robust. FEC encoding of the data units is compatible with the current embodiment.

In a further implementation form of the first aspect, the sending device is configured to: the indication of the scrambling seed is encoded using a block code.

Thus, the indication is encoded differently than the data units, which is particularly simple and more robust. FEC encoding of the data units is compatible with the current embodiment.

In a further implementation form of the first aspect, the sending device is configured to: the indication of the scrambling seed is encoded using a Hadamard code as a generator matrix.

In a further implementation form of the first aspect, the sending device is configured to: the indication of the scrambling seed is modulated using Binary Phase Shift Keying (BPSK).

Therefore, emphasis is given to the indication, making it less prone to error.

A second aspect of the present invention provides a receiving apparatus for supporting HARQ, the receiving apparatus being configured to: the method may include receiving an indication of a scrambling seed from a transmitting device, then receiving at least one scrambled and encoded data unit separated from the indication of the scrambling seed, descrambling the scrambled and encoded data unit based on the scrambling seed determined from the indication of the scrambling seed, and decoding the encoded data unit using FEC decoding.

Thus, unlike current receiver implementations, FEC decoding is performed after descrambling, i.e., an FEC decoder may be arranged after the descrambler. In this way, with a varying (e.g., random) scrambling seed, a combination of multiple transmissions becomes possible. Furthermore, by receiving an indication of the scrambling seed separated from the data unit, the indication can be decoded in a more robust manner, thereby reducing decoding errors.

In one implementation form of the second aspect, the receiving device is configured to: sending an Acknowledgement (ACK) and/or a negative acknowledgement (Not acknowledgement, NACK) message to the sending device regarding at least one correctly and/or incorrectly decoded data unit, receiving a further indication of a scrambling seed from the sending device if the decoding of the at least one data unit fails (105), then receiving a scrambled and coded retransmission of the failed data unit separated from the further indication of the scrambling seed, descrambling the scrambled and coded retransmission of the failed data unit based on the scrambling seed determined from the further indication of the scrambling seed, decoding the coded retransmission of the failed data unit using FEC decoding, and soft combining the retransmission of the failed data unit with the previously received failed data unit.

Thus, the receiving device is configured to support and perform HARQ, especially for Wi-Fi.

In a further implementation form of the second aspect, the receiving device is configured to: an indication of a received scrambling seed separated from the received scrambled and encoded data units, respectively, is decoded and/or demodulated.

In a further implementation form of the second aspect, the receiving device is configured to: an indication of a scrambling seed is obtained from predetermined bits of one or more signaling fields received by a transmitting device.

In a further implementation form of the second aspect, the receiving device is configured to: extracting an indication of a scrambling seed from a PHY preamble, in particular from a SIG-A field or a SIG-B field received by the transmitting device.

By means of the above-described implementation forms, the advantages described for the corresponding implementation forms of the transmitting device are achieved.

A third aspect of the present invention provides a method for supporting HARQ, the method comprising: the method includes encoding at least one data unit using FEC encoding, scrambling the encoded data unit based on a scrambling seed, providing an indication of the scrambling seed separate from the scrambled and encoded data unit, and transmitting the indication of the scrambling seed, and then transmitting the scrambled and encoded data unit.

In one implementation form of the third aspect, the method comprises: an indication of a scrambling seed separated from at least one data unit is encoded and/or modulated.

In a further implementation form of the third aspect, the method comprises: an indication of the scrambling seed is included in the PHY preamble.

In a further implementation form of the third aspect, the method comprises: an indication of a scrambling seed is included in the SIG-A field or the SIG-B field.

In a further implementation form of the third aspect, the method comprises: the indication of the scrambling seed is defined based on predetermined bits of one or more signaling fields.

In a further implementation form of the third aspect, the method comprises: the indication of the scrambling seed is encoded using BCC.

In a further implementation form of the third aspect, the method comprises: the indication of the scrambling seed is encoded using a block code.

In a further implementation form of the third aspect, the method comprises: the indication of the scrambling seed is encoded using a Hadamard code as a generator matrix.

In a further implementation form of the third aspect, the method comprises: the indication of the scrambling seed is modulated using BPSK.

With the method of the third aspect, the advantages and effects described above with respect to the transmitting device of the first aspect are achieved.

A fourth aspect of the present invention provides a method for supporting HARQ, the method comprising: receiving an indication of a scrambling seed, then receiving at least one scrambled and encoded data unit separated from the indication (105) of the scrambling seed (104), descrambling the scrambled and encoded data unit based on the scrambling seed determined from the indication of the scrambling seed, and decoding the encoded data unit using FEC decoding.

In one implementation form of the fourth aspect, the method comprises: transmitting an Acknowledgement (ACK) and/or a Negative Acknowledgement (NACK) message to the transmitting device regarding the at least one correctly and/or incorrectly decoded data unit, receiving a further indication of the scrambling seed from the transmitting device if the decoding of the at least one data unit fails, then receiving a scrambled and encoded retransmission of the failed data unit separated from the further indication of the scrambling seed, descrambling the scrambled and encoded retransmission of the failed data unit based on the scrambling seed determined from the further indication of the scrambling seed, decoding the encoded retransmission of the failed data unit using FEC decoding, and soft combining the retransmission of the failed data unit with the previously received failed data unit.

In a further implementation form of the fourth aspect, the method comprises: an indication of a received scrambling seed separated from the received scrambled and encoded data units, respectively, is decoded and/or demodulated.

In a further implementation form of the fourth aspect, the method comprises: an indication of a scrambling seed is obtained from a predetermined bit of the received one or more signaling fields.

In a further implementation form of the fourth aspect, the method comprises: an indication of the scrambling seed is extracted from the PHY preamble, in particular from the received SIG-a field or SIG-B field.

With the method of the fourth aspect, the advantages and effects described above with respect to the receiving device of the second aspect are achieved.

In summary, embodiments (aspects and implementations) of the present invention are based on performing scrambling after FEC encoding and descrambling before FEC decoding. The results were:

the scrambling seed can be changed every time (HARQ) retransmission-and the scrambled LLRs can be combined-for better detection.

The scrambling seed is separate from the data unit, making it more robust.

The data unit does not need to be periodically aligned with the scrambling sequence (in HARQ mode) and can still be aligned with the FEC packet length.

If the scrambling seed is not separated, then in case of retransmission of a non-first data unit (to become first), the scrambling seed must be included in the first retransmitted data unit, thus altering the coded bits.

It has to be noted that all devices, elements, units and means described in the present application may be implemented as software or hardware elements or any kind of combination thereof. All steps performed by the various entities described in this application, as well as the functions described as being performed by the various entities, are intended to mean that the various entities are adapted or configured to perform the various steps and functions. Even though in the following description of certain embodiments certain functions or steps performed by external entities are not reflected in the description of certain detailed means of the entity performing the certain steps or functions, a person skilled in the art shall realize these methods and functions in corresponding software or hardware elements or any kind of combination thereof.

Drawings

The above aspects and implementations of the invention are explained in the following description of the embodiments with reference to the drawings, in which

Fig. 1 shows a transmitting device according to an embodiment of the present invention.

Fig. 2 shows a method according to an embodiment of the invention.

Fig. 3 shows a receiving device according to an embodiment of the invention.

Fig. 4 shows a method according to an embodiment of the invention.

Fig. 5 shows a generator matrix.

Fig. 6 shows a parity check matrix.

Fig. 7 shows a block diagram of a conventional 802.11n transmitter.

Fig. 8 shows a block diagram of a conventional 802.11ax transmitter.

Detailed Description

Fig. 1 shows a transmitting device 100 according to an embodiment of the invention. The transmitting device 100 is used to support HARQ, especially HARQ for IEEE 802.11/Wi-Fi. This means that the device 100 may be an 802.11 standard transmitting device that supports HARQ.

The transmitting device 100 is configured to encode the at least one data unit 101 using FEC encoding 102 to obtain at least one encoded data unit 101. The FEC encoding 102 may be performed by a conventional FEC encoder, for example, in a conventional transmitter as shown in fig. 7. The data unit 101 may be an MPDU and if multiple data units 101 are encoded, the data units 101 may be in an a-MPDU, i.e., may form a PPDU.

Furthermore, the transmitting device 100 is configured to scramble the encoded data unit 103 based on the scrambling seed 104 to obtain at least one scrambled and encoded data unit 106. The scrambling may be performed by a scrambler, which is correspondingly located in the device 100 after the FEC encoder performing the FEC encoding 102. The scrambling seed 104 may comprise a sequence of bits that serves as an input to the scrambler of the encoded data unit 103.

The transmitting device 100 is then arranged to provide an indication 105 of the scrambling seed 104 separated from the scrambled and encoded data unit 106. The indication 105 may be designed such that the scrambling seed 104 may be obtained based on the indication 105, e.g. may be calculated or derived from the indication 105.

Finally, the transmitting device 100 is arranged to transmit an indication 105 of the scrambling seed 104 and then, i.e. after transmitting the indication, to transmit the scrambled and encoded data unit 106 directly or indirectly to the receiving device 300.

Fig. 2 shows a corresponding method 200 according to an embodiment of the invention, which method 200 can accordingly be performed by the transmitting device 100 of fig. 1. The method 200 is for supporting HARQ, especially for Wi-Fi.

The method 200 comprises the following steps: step 201, encoding at least one data unit 101 by using FEC encoding 102; step 202, scrambling the encoded data unit 103 based on the scrambling seed 104; step 203, providing an indication 105 of a scrambling seed 104 separated from the scrambled and encoded data unit 106; and step 204: an indication 105 of the scrambling seed 104 is sent, followed by a scrambled and encoded data unit 106.

Fig. 3 shows a receiving device 300 according to an embodiment of the invention. The receiving device 300 is for HARQ support, in particular for IEEE 802.11/Wi-Fi, i.e. the device 300 may be an 802.11 standard receiving device supporting HARQ.

The receiving device 300 is arranged to receive the indication 105 of the scrambling seed 104 from the transmitting device 100 and then, i.e. after receiving the indication 105, to receive the at least one scrambled and encoded data unit 106 separated from the indication 105 of the scrambling seed 104. The transmitting device 100 is the device shown in fig. 1.

The receiving device 300 is further configured to descramble the scrambled and encoded data unit 106 based on the scrambling seed 104 determined from the indication 105 of the scrambling seed 104 in order to obtain at least one encoded data unit 103. Descrambling may be performed by a descrambler, such as provided by a conventional receiver.

Furthermore, the receiving device 300 is configured to decode the encoded data unit 103 using FEC decoding 301 to obtain at least one data unit 101. The data units 101 may also be MPDUs and the further data units 101 may be a-MPDUs or PPDUs. The FEC decoding 301 may be performed by a conventional FEC decoder arranged after the descrambler performing the descrambling.

Fig. 4 shows a corresponding method 400 according to an embodiment of the invention, which method 400 may accordingly be performed by the receiving device 300 in fig. 3. The method 400 is for supporting HARQ, especially for WIFI.

The method 400 includes: step 401, receiving an indication 105 of a scrambling seed 104, and then receiving at least one scrambled and encoded data unit 106 separated from the indication 105 of the scrambling seed 104; a step 402 of descrambling 402 the scrambled and encoded data unit 106 based on the scrambling seed 104 determined from the indication 105 of the scrambling seed 104; at step 403, the encoded data unit 103 is decoded using FEC decoding 301.

In the following, more details regarding the above-described apparatuses 100 and 300 are provided, corresponding to the methods 200 and 400, respectively. In particular, different solutions for implementing two main aspects of embodiments of the present invention are proposed, namely:

first, in comparison with the conventional transmitter, the switching of the positions/orders of the FEC encoding 102(FEC encoder) and the scrambling (scrambler) in the transmitting apparatus 100, i.e., the scrambler is located after the FEC encoder to operate on the encoded bits of the data unit. Also, in contrast to conventional receivers, the switching of the position/order of the descrambling (descrambler) and FEC decoding 301(FEC decoder) in the receiving device 300, i.e. the descrambler is located before the FEC decoder, so that the descrambler operates on the encoded bits of the data unit 101.

Second, an indication 105 of the scrambling seed 104 (e.g., the SERVICE field that is typically used) is separated from the data unit 101. That is, the indication 105 is either provided in a different transmission part than the data unit 101 or is encoded and/or modulated differently than the data unit 101.

Since it is preferred that the scrambling seed 104 is changed at each (re-) transmission while still transmitting the same code word (up to the redundancy version), the scrambling operates on the basis of the coded bits of the data unit 101 in the transmitting device 100. This allows the LLRs ("soft bits") on the receiving device 300 to be descrambled before combining. This is true for both BCC and LDPC. Thus, an indication 105 (e.g., a SERVICE field) of the scrambling seed 104 is provided separately by the data unit 101. The transmitting device 100 indicates 105 the scrambling seed 104 to the receiving device 300 before the data unit.

A first choice for indicating the scrambling seed 104 is now described. In particular, a very simple scheme is to remove the indication 105 (e.g., the entire SERVICE field) from its current location (prior to the data portion) and move the scrambling seed indication 105 to the PHY preamble. That is, the transmitting device 100 may be configured to include the indication 105 of the scrambling seed 104 in the PHY preamble, and accordingly, the receiving device 300 may be configured to extract the indication 105 of the scrambling seed 104 from the PHY preamble. The PHY preamble is a portion of the transmission that is different from the data portion (one or more data units).

For example, a scrambling seed (which may be 7 bits) may be indicated 105 within SIG-a (for all STAs) or within SIG-B (for each STA). This means that the transmitting device 100 may be configured to include the indication 105 of the scrambling seed 104 in the SIG-a field or the SIG-B field, and accordingly the receiving device 300 may be configured to extract the indication 105 of the scrambling seed 104 from the SIG-a field or the SIG-B field received by the transmitting device 100. This is a simple solution but requires some overhead.

Alternatively, existing fields (e.g., some combination of bits representing STA-ID and SIG-B Cyclic Redundancy Check (CRC) of STA length, 7 Least Significant Bits (LSB) of length L-SIG) may be used to generate a new (e.g., pseudo-random scrambling seed 104) (e.g., using a predefined recipe (hence known to both transmitting device 100 and receiving device 300)). That is, the transmitting device 100 may be used to define the indication 105 of the scrambling seed 104 based on predetermined bits of one or more signaling fields, and the receiving device 300 may be used accordingly for the indication 105 of the scrambling seed 104 derived from the predetermined bits of the one or more signaling fields received by the transmitting device 100.

A second option for indicating the scrambling seed 104 is now described. In particular, the indication 105 (e.g., the SERVICE field) may remain intact and be maintained in a regular position, but may be encoded and/or modulated separately from the data unit(s) 101 in the transmitting device 100, such that the receiving device 300 may decode and/or demodulate the data unit(s) separately from it, may obtain the descrambling seed 104, and may be immediately available for use on LLRs.

For example, BCC coding may be used. If BCC is used (and thus Viterbi decoding is used), an additional indication 105 (e.g. a SERVICE field or seed information) may be needed to ensure that the Viterbi decoder has sufficient depth.

A third option for indicating the scrambling seed 104 is now described. Specifically, indication 105 (e.g., the SERVICE field) may remain intact and be maintained in a regular position, but may be encoded and/or modulated separately from data unit 101. For example, to ensure maximum robustness, BPSK Modulation with some block code encoding (e.g., rate 1/2) may be used regardless of the Modulation and Coding Scheme (MCS) used for the data units 101. Therefore, the indication 105(SERVICE field) is always coded and modulated using a non-robust scheme.

This means that the number of tones allocated to the indication 105 (e.g., SERVICE field) is always fixed, and thus it is easy to calculate the number of tones required for the data unit 101, LDPC parameters (shortening/puncturing/repetition), pre-FEC (pre-FEC) bits, and so on. A simple block code may be used. For example, a systematic linear block code with a code rate of 1/2 may be used, where the scrambling seed 104 is appended with 1 bit (making it 8 bits), and a Hadamard code may be used to generate the matrix 500, as shown in fig. 5. The parity check matrix is shown in fig. 7.

The invention has been described in connection with various illustrative embodiments and implementations. However, other variations will be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the independent claims. In the claims as well as in the description, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.