WO2007017827A1

WO2007017827A1 - Device for receiving symbols in subcarriers

Info

Publication number: WO2007017827A1
Application number: PCT/IB2006/052712
Authority: WO
Inventors: Manel Collados
Original assignee: Nxp B.V.
Priority date: 2005-08-10
Filing date: 2006-08-07
Publication date: 2007-02-15
Also published as: EP1917771A1; JP2009505474A; CN101238695A

Abstract

In devices (1) comprising transmitters (10) and receivers (20), the transmitters (10) are provided with buffering means for allocating buffered third / fourth symbols to fifth and sixth / seventh and eighth subcarriers, the fifth and sixth and seventh and eighth subcarriers being different subcarriers in a same time slot, and the receivers (20) are provided with derivation means for deriving first / second symbols from first and second / third and fourth subcarriers, the first and second and third and fourth subcarriers being different subcarriers in a same time slot. Then, the symbols are each present twice or more in a collection of subcarriers. As a result, simple and more robust devices (1) have been created. The subcarriers may be orthogonal frequency division multiplexing subcarriers and the symbols may be phase shift keying symbols. The subcarriers carrying the same symbol may be non-neighboring subcarriers, to increase a robustness. The buffering means comprise a buffer (14) and the derivation means comprise a combiner (24).

Description

Device for receiving symbols in subcarriers

The invention relates to a device comprising a receiver, and also relates to a receiver, to a receiving computer program product, to a transmitter, to a transmitting computer program product, to a method and to a signal.

Examples of such devices are mobile and wireless consumer products and mobile and wireless interfaces.

US 2003/0169681 Al discloses multi-carrier communications with group- based subcarrier allocation. For a system employing orthogonal frequency division multiple access, subcarriers are partioned into groups of at least one cluster of subcarriers. At least one cluster of subcarriers is used for a communication with a subscriber.

The known device is disadvantageous, inter alia, owing to the fact that it is relatively non-robust. The receiver cannot receive a subcarrier that has gone lost in noise.

It is an object of the invention, inter alia, to provide a device that is relatively robust. Further objects of the invention are, inter alia, to provide a receiver, a receiving computer program product, a transmitter, a transmitting computer program product, a method and a signal that are relatively robust. The device according to the invention comprises a receiver for receiving symbols in subcarriers from a further device, the receiver comprising derivation means for deriving a first symbol from a first subcarriers and for deriving the first symbol from a second subcarrier and for deriving a second symbol from a third subcarrier and for deriving the second symbol from a fourth subcarrier, the first and second and third and fourth subcarriers being different subcarriers in a same time slot.

So, one first symbol is no longer present only once in a collection of subcarriers but this one first symbol is present twice (or three times, or four times etc.) in this collection of subcarriers. And one second symbol is no longer present only once in a collection of subcarriers but this one second symbol is present twice (or three times, or four times etc.) in this collection of subcarriers. This can be done in a relatively simple way. As a result, a more robust and simple device has been created. Its robustness is based on the fact that one and the same symbol is received twice or more, and that offers the possibility to compare, select and/or combine the different receptions of this same symbol. Its simplicity is based on the fact that it is relatively simple to insert one and the same buffered symbol into two or more different subcarriers.

The invention is further advantageous, inter alia, in that the device according to the invention can be very easily implemented, without much extra effort, in a standard compliant system. The symbol periods of a first number of symbols in a second number of subcarriers are for example parallel symbol periods located in said time slot or coinciding with said time slot, the first number being smaller than the second number.

An embodiment of the device according to the invention is defined by the subcarriers being orthogonal frequency division multiplexing subcarriers and/or the symbols being phase shift keying symbols. For example at 6 Mb/s and 9 Mb/s, quadrature phase shift keying symbols having coding rates of ¹A and % might be used. Of the 64 available subcarriers, 48 subcarriers are used for carrying symbols, whereby according to the invention for example 24 symbols are to be inserted twice each, or 16 symbols are to be inserted three times each, or 12 symbols are to be inserted four times each etc. So, preferably, each symbol present in a collection of subcarriers is present twice, three times, four times etc. without however excluding other options.

An embodiment of the device according to the invention is defined by the derivation means being spreading-code-less. A use of spreading codes makes the device unnecessarily complex.

An embodiment of the device according to the invention is defined by the first and second subcarriers being non-neighboring subcarriers and the third and fourth subcarriers being non-neighboring subcarriers. By creating distances between the subcarriers that carry the same symbol, the transmitting device according to the invention has become even more robust. The larger the distance, the better the robustness.

An embodiment of the device according to the invention is defined by the receiver comprising a serial circuit of a front end, a guard interval remover, a fast fourier transformer and a demapper, the derivation means comprising a combiner located between the fast fourier transformer and the demapper, the receiver further comprising a controller for controlling the fast fourier transformer and the combiner and the demapper for deriving the first symbol from the first and second subcarriers and for deriving the second symbol from the third and fourth subcarriers. Such a combiner forms a simple embodiment of the derivation means, without excluding other embodiments such as switches etc. The derivation means and/or the combiner may be based on maximum ratio combining where symbol pairs are scaled according to their respective channel gain before being added. An embodiment of the device according to the invention is defined by a transmitter for transmitting symbols in subcarriers to the further device, the transmitter comprising buffering means for allocating a buffered third symbol to a fifth subcarrier and for allocating the buffered third symbol to a sixth subcarrier and for allocating a buffered fourth symbol to a seventh subcarrier and for allocating the buffered fourth symbol to an eighth subcarrier, the fifth and sixth and seventh and eighth subcarriers being different subcarriers in a same time slot. Again, one third symbol is no longer present only once in a collection of subcarriers but this one third symbol is present twice (or three times, or four times etc.) in this collection of subcarriers. And one fourth symbol is no longer present only once in a collection of subcarriers but this one fourth symbol is present twice (or three times, or four times etc.) in this collection of subcarriers.

It should be noted that US 2003/0112744 Al discloses in its paragraphs 0001- 0004 a multi-carrier wireless communication system based on a multi-carrier modulation scheme such as orthogonal frequency division multiplexing. A high-order modulation and a high code rate is assigned in case of a high signal to interference plus noise ratio, and a low- order modulation and a low code rate is assigned in case of a low signal to interference plus noise ratio. US 2003/0112744 Al discloses in its Figure 3 a transmitter based on spreading code technology, which is relatively complex and designed for digital signal processors which are relatively slow compared to application specific integrated circuits. US 2003/0112744 Al does not disclose any receiver technology. An embodiment of the device according to the invention is defined by the subcarriers being orthogonal frequency division multiplexing subcarriers and/or the symbols being phase shift keying symbols.

An embodiment of the device according to the invention is defined by the buffering means being spreading-code-less. An embodiment of the device according to the invention is defined by the fifth and sixth subcarriers being non-neighboring subcarriers and the seventh and eighth subcarriers being non-neighboring subcarriers.

An embodiment of the device according to the invention is defined by the transmitter comprising a serial circuit of a mapper, an inverse fast fourier transformer, a guard interval inserter and a front end, the buffering means comprising a buffer located between the mapper and the inverse fast fourier transformer, the transmitter further comprising a controller for controlling the mapper, the buffer and the inverse fast fourier transformer for allocating the buffered third symbol to the fifth and sixth subcarriers and for allocating the buffered fourth symbol to the seventh and eighth subcarriers. Such a buffer forms a simple embodiment of the buffering means, without excluding other embodiments such as switches etc.

Embodiments of the receiver according to the invention and of the receiving computer program product according to the invention and of the transmitter according to the invention and of the transmitting computer program product according to the invention and of the method according to the invention and of the signal according to the invention correspond with the embodiments of the device according to the invention. The computer program products according to the invention might comprise and/or be stored on a medium for storing computer program products. The invention is based upon an insight, inter alia, that a clustering of subcarriers can be used for other purposes than subscriber allocation, and is based upon a basic idea, inter alia, that two or more subcarriers might be used for exchanging the same symbol twice or more in one time slot or in one symbol period.

The invention solves the problem, inter alia, to provide a device that is relatively robust, and is further advantageous, inter alia, in that the device according to the invention can be very easily implemented, without much extra effort, in a standard compliant system.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments(s) described hereinafter.

In the drawings:

Fig. 1 shows diagrammatically two devices according to the invention each comprising a receiver according to the invention and a transmitter according to the invention, and

Fig. 2 shows diagrammatically a device according to the invention comprising a receiver according to the invention and a transmitter according to the invention in greater detail. The device 1 according to the invention shown in Fig. 1 comprises a transmitter 10 according to the invention and a receiver 20 according to the invention. The device 2 according to the invention shown in Fig. 1 comprises a transmitter 30 according to the invention and a receiver 40 according to the invention.

The device 1 according to the invention shown in Fig. 2 comprises a transmitter 10 according to the invention and a receiver 20 according to the invention both shown in greater detail. The transmitter 10 is coupled to a baseband unit 18. The transmitter 10 comprises a serial circuit of a coder/puncturer 12, a mapper 13, a buffer 14, an inverse fast fourier transformer 15, a guard interval inserter 16 and a front end 17. The transmitter 10 further comprises a controller 11 coupled to the baseband unit 18 and further for example coupled to the coder/puncturer 12, the mapper 13, the buffer 14, the inverse last fourier transformer 15, the guard interval inserter 16 and the front end 17. The buffer 14 forms a possible embodiment for buffering means for allocating a buffered third symbol to a fifth subcarrier and for allocating the buffered third symbol to a sixth subcarrier and for allocating a buffered fourth symbol to a seventh subcarrier and for allocating the buffered fourth symbol to an eighth subcarrier, the fifth and sixth and seventh and eighth subcarriers being different subcarriers in a same time slot, under control of the controller 11.

By introducing the buffering means in the form of the buffer 14 or alternatively in the form of buffering switches, one third symbol is no longer present only once in a collection of subcarriers but this one third symbol is present twice (or three times, or four times etc.) in this collection of subcarriers. And one fourth symbol is no longer present only once in a collection of subcarriers but this one fourth symbol is present twice (or three times, or four times etc.) in this collection of subcarriers. As a result, a simple and more robust device 1 has been created.

The receiver 20 is coupled to a baseband unit 28. The receiver 20 comprises a serial circuit of a front end 27, a guard interval remover 26, a fast fourier transformer 25, a combiner 24, a demapper 23 and a decoder/depuncturer 22. Between the fast fourier transformer 25 and the combiner 24, a channel compensator not shown may further be present. This channel compensator may alternatively be included in the combiner 24. The receiver 20 further comprises a controller 21 coupled to the baseband unit 28 and further for example coupled to the decoder/depuncturer 22, the demapper 23, the combiner 24, the fast fourier transformer 25, the guard interval remover 26 and the front end 27. The combiner 24 forms a possible embodiment for derivation means for deriving a first symbol from a first subcarrier and for deriving the first symbol from a second subcarrier and for deriving a second symbol from a third subcarrier and for deriving the second symbol from a fourth subcarrier, the first and second and third and fourth subcarriers being different subcarriers in a same time slot, under control of the controller 21. By introducing the derivation means in the form of the combiner 24 or alternatively in the form of deriving switches, one first symbol is no longer present only once in a collection of subcarriers but this one first symbol is present twice (or three times, or four times etc.) in this collection of subcarriers. And one second symbol is no longer present only once in a collection of subcarriers but this one second symbol is present twice (or three times, or four times etc.) in this collection of subcarriers. As a result, a simple and more robust device 1 has been created. The derivation means and/or the combiner 24 may be based on maximum ratio combining where symbol pairs are scaled according to their respective channel gain before being added.

The subcarriers may be orthogonal frequency division multiplexing subcarriers and/or the symbols may be phase shift keying symbols. For example at 6 Mb/s and 9 Mb/s, quadrature phase shift keying symbols having coding rates of ¹A and % might be used. Of the 64 available subcarriers, 48 subcarriers are used for carrying symbols, whereby according to the invention for example 24 symbols are to be inserted/derived twice each, or 16 symbols are to be inserted/derived three times each, or 12 symbols are to be inserted/derived four times each etc. So, preferably, each symbol present in a collection of subcarriers is present twice, three times, four times etc. without however excluding other options.

The buffering means and the derivation means are preferably spreading-code- less, to keep them simple and robust. The standard may be one from a IEEE 802 family. The first and second subcarriers may be non-neighboring subcarriers and the third and fourth subcarriers may be non-neighboring subcarriers. The fifth and sixth subcarriers may be non-neighboring subcarriers and the seventh and eighth subcarriers may be non-neighboring subcarriers. By creating distances between the subcarriers that carry the same symbol, the device 1 has become even more robust. The larger the distance, the better the robustness.

In the Figures, each block shown may be at least partly hardware, at least partly software of a mixture of both and may be divided into two or more (smaller) blocks, and any two or more blocks shown may be combined into a (larger) block, without departing from the scope of this invention. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. 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.

Claims

CLAIMS:

1. Device (1) comprising a receiver (20) for receiving symbols in subcarriers from a further device (2), the receiver (20) comprising derivation means for: deriving a first symbol from a first subcarrier, for deriving the first symbol from a second subcarrier, - for deriving a second symbol from a third subcarrier, and for deriving the second symbol from a fourth subcarrier, the first and second and third and fourth subcarriers being different subcarriers in a same time slot.

2. Device (1) according to claim 1, the subcarriers being orthogonal frequency division multiplexing subcarriers and/or the symbols being phase shift keying symbols.

3. Device (1) according to claim 1, the derivation means being spreading-code- less.

4. Device (1) according to claim 1, the first and second subcarriers being non- neighboring subcarriers and the third and fourth subcarriers being non-neighboring subcarriers.

5. Device (1) according to claim 1, the receiver (20) comprising a serial circuit of a front end (27), a guard interval remover (26), a fast fourier transformer (25) and a demapper (23), the derivation means comprising a combiner (24) located between the fast fourier transformer (25) and the demapper (23), the receiver (20) further comprising a controller (21) for controlling the fast fourier transformer (25) and the combiner (24) and the demapper (23) for deriving the first symbol from the first and second subcarriers and for deriving the second symbol from the third and fourth subcarriers.

6. Device (1) according to claim 1, further comprising a transmitter (10) for transmitting symbols in subcarriers to the further device (2), the transmitter (10) comprising buffering means for allocating a buffered third symbol to a fifth subcarrier and for allocating the buffered third symbol to a sixth subcarrier and for allocating a buffered fourth symbol to a seventh subcarrier and for allocating the buffered fourth symbol to an eighth subcarrier, the fifth and sixth and seventh and eighth subcarriers being different subcarriers in a same time slot.

7. Device (1) according to claim 6, the subcarriers being orthogonal frequency division multiplexing subcarriers and/or the symbols being phase shift keying symbols.

8. Device (1) according to claim 6, the buffering means being spreading-code- less.

9. Device (1) according to claim 6, the fifth and sixth subcarriers being non- neighboring subcarriers and the seventh and eighth subcarriers being non-neighboring subcarriers.

10. Device (1) according to claim 6, the transmitter (10) comprising a serial circuit of a mapper (13), an inverse fast fourier transformer (15), a guard interval inserter (16) and a front end (17), the buffering means comprising a buffer (14) located between the mapper (13) and the inverse fast fourier transformer (15), the transmitter (10) further comprising a controller (11) for controlling the mapper (13), the buffer (14) and the inverse fast fourier transformer (15) for allocating the buffered third symbol to the fifth and sixth subcarriers and for allocating the buffered fourth symbol to the seventh and eighth subcarriers.

11. Receiver (20) for receiving symbols in subcarriers from a further transmitter

(30), the receiver (20) comprising derivation means for deriving a first symbol from a first subcarrier and for deriving the first symbol from a second subcarrier and for deriving a second symbol from a third subcarrier and for deriving the second symbol from a fourth subcarrier, the first and second and third and fourth subcarriers being different subcarriers in a same time slot.

12. Receiving computer program product for performing a fast fourier transforming function and a combining function and a demapping function and a controlling function for controlling the fast fourier transforming function and the combining function and the demapping function for deriving a first symbol from a first subcarrier and for deriving the first symbol from a second subcarrier and for deriving a second symbol from a third subcarrier and for deriving the second symbol from a fourth subcarrier, the first and second and third and fourth subcarriers being different subcarriers in a same time slot.

13. Transmitter (10) for transmitting symbols in subcarriers to a further receiver (40), the transmitter (10) comprising buffering means for allocating a buffered third symbol to a fifth subcarrier and for allocating the buffered third symbol to a sixth subcarrier and for allocating a buffered fourth symbol to a seventh subcarrier and for allocating the buffered fourth symbol to an eighth subcarrier, the fifth and sixth and seventh and eighth subcarriers being different subcarriers in a same time slot.

14. Transmitting computer program product for performing a mapping function and a buffering function and an inverse fast fourier transforming function and a controlling function for controlling the mapping function and the buffering function and the inverse fast fourier transforming function for allocating a buffered third symbol to a fifth subcarrier and for allocating the buffered third symbol to a sixth subcarrier and for allocating a buffered fourth symbol to a seventh subcarrier and for allocating the buffered fourth symbol to an eighth subcarrier, the fifth and sixth and seventh and eighth subcarriers being different subcarriers in a same time slot.

15. Method for exchanging symbols in subcarriers between a transmitter (10,30) and a receiver (40,20), the method comprising the steps of: allocating a first symbol to a first subcarrier, via buffering means - allocating the first symbol to a second subcarrier, via said buffering means allocating a second symbol to a third subcarrier, via said buffering means, and allocating the second symbol to a fourth subcarrier, via said buffering means, deriving the first symbol from the first and second subcarriers, via derivation means, - deriving the second symbol from the third and fourth subcarriers, via said derivation means, the first and second and third and fourth subcarriers being different subcarriers in a same time slot.

16. Signal comprising symbols in subcarriers, a first symbol being allocated to a first subcarrier and the first symbol being allocated to a second subcarrier and a second symbol being allocated to a third subcarrier and the second symbol being allocated to a fourth subcarrier via buffering means, and the first symbol being derivable from the first and second subcarriers and the second symbol being derivable from the third and fourth subcarriers via derivation means, the first and second and third and fourth subcarriers being different subcarriers in a same time slot.