US20080069255A1  Efficient Bit Interleaver for A MultiBand OFDM UltraWideband System  Google Patents
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 US20080069255A1 US20080069255A1 US11/939,222 US93922207A US2008069255A1 US 20080069255 A1 US20080069255 A1 US 20080069255A1 US 93922207 A US93922207 A US 93922207A US 2008069255 A1 US2008069255 A1 US 2008069255A1
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 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L1/00—Arrangements for detecting or preventing errors in the information received
 H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
 H04L1/0056—Systems characterized by the type of code used
 H04L1/0059—Convolutional codes

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 H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
 H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
 H03M13/27—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques
 H03M13/2703—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes using interleaving techniques the interleaver involving at least two directions
 H03M13/2707—Simple rowcolumn interleaver, i.e. pure block interleaving

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04B—TRANSMISSION
 H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00  H04B13/00; Details of transmission systems not characterised by the medium used for transmission
 H04B1/69—Spread spectrum techniques
 H04B1/7163—Spread spectrum techniques using impulse radio
 H04B1/7176—Data mapping, e.g. modulation

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04B—TRANSMISSION
 H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00  H04B13/00; Details of transmission systems not characterised by the medium used for transmission
 H04B1/69—Spread spectrum techniques
 H04B1/7163—Spread spectrum techniques using impulse radio
 H04B1/719—Interferencerelated aspects

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 H04L1/0056—Systems characterized by the type of code used
 H04L1/0071—Use of interleaving

 H—ELECTRICITY
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 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L5/00—Arrangements affording multiple use of the transmission path
 H04L5/003—Arrangements for allocating subchannels of the transmission path
 H04L5/0042—Arrangements for allocating subchannels of the transmission path intrauser or intraterminal allocation

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L5/00—Arrangements affording multiple use of the transmission path
 H04L5/003—Arrangements for allocating subchannels of the transmission path
 H04L5/0044—Arrangements for allocating subchannels of the transmission path allocation of payload

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
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 H04L5/00—Arrangements affording multiple use of the transmission path
 H04L5/003—Arrangements for allocating subchannels of the transmission path
 H04L5/0078—Timing of allocation
 H04L5/0082—Timing of allocation at predetermined intervals
 H04L5/0083—Timing of allocation at predetermined intervals symbolbysymbol

 H—ELECTRICITY
 H04—ELECTRIC COMMUNICATION TECHNIQUE
 H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
 H04L5/00—Arrangements affording multiple use of the transmission path
 H04L5/0001—Arrangements for dividing the transmission path
 H04L5/0003—Twodimensional division
 H04L5/0005—Timefrequency
 H04L5/0007—Timefrequency the frequencies being orthogonal, e.g. OFDM(A), DMT
Abstract
An efficient bit interleaving scheme for a multiband OFDM ultrawideband (UWB) system. The encoded bits of the multiband OFDM system are interleaved within each OFDM symbol and across OFDM symbols. The bit interleaving scheme minimizes performance degradation due to groups of contiguous OFDM tones experiencing a poor SNR caused by the frequency selective channel, exploits the frequency diversity across subbands, randomizes the effect of cochannel interference from simultaneously operating uncoordinated piconets, and randomizes the impact of generic narrowband interferers present within the UWB spectrum.
Description
 The application claims priority under 35 U.S.C. § 119(e)(1) of provisional application Ser. No. 60/453,871, attorney docket number TI36096PS, entitled Efficient Bit Interleaver For A TFIOFDM UltraWideband System, filed Mar. 11, 2003, by Jaiganesh Balakrishnan, Anuj Batra and Anand Dabak.
 1. Field of the Invention
 This invention relates generally to multiband systems for ultra wideband (UWB) applications, and more specifically to a technique for implementing efficient bit interleaving for a UWB system employing multiband orthogonal frequency division multiplexing (OFDM).
 2. Description of the Prior Art
 The encoded bits in a multiband OFDM system are grouped into OFDM symbols, and each symbol is transmitted over different frequency subbands. The UWB multipath channel is frequency selective and exhibits significant gain (or attenuation) variations across tones and subbands. This results in unequal error protection for the encoded bits transmitted across the various tones and subbands.
 In view of the above, it would be both advantageous and desirable to provide a bit interleaving scheme that minimizes performance degradation due to groups of contiguous OFDM tones experiencing a poor SNR caused by the frequency selective channel, exploits the frequency diversity across subbands, randomizes the effect of cochannel interference from simultaneously operating uncoordinated piconets, and randomizes the impact of generic narrowband interferers present within the UWB spectrum.
 The present invention is directed to an efficient bit interleaving scheme for a multiband OFDM ultrawideband (UWB) system. The encoded bits of the multiband OFDM system are interleaved within each OFDM symbol and across OFDM symbols. The bit interleaving scheme minimizes performance degradation due to groups of contiguous OFDM tones experiencing a poor SNR caused by the frequency selective channel, exploits the frequency diversity across subbands, randomizes the effect of cochannel interference from simultaneously operating uncoordinated piconets, and randomizes the impact of generic narrowband interferers present within the UWB spectrum.
 According to one embodiment, a bit interleaving method comprises the steps of
 grouping the coded bits of an OFDM symbol stream into blocks of XN_{CBPS}, wherein X is a desired number of OFDM symbols and further wherein N_{CBPS }is the number of coded bits per symbol;
 permuting each group of coded bits and generating interleaved OFDM symbols in response thereto only if the coded bits available for grouping correspond to no less than X OFDM symbols;
 grouping the interleaved OFDM symbols into blocks of N_{CBPS }bits; and
 permuting each block of N_{CBPS }bits associated with the interleaved OFDM symbols and generating interleaved OFDM tones in response thereto.
 According to another embodiment, a bit interleaving method comprises the steps of
 grouping the coded bits of an OFDM symbol stream into blocks of XN_{CBPS}, wherein X is a desired number of OFDM symbols and further wherein N_{CBPS }is the number of coded bits per symbol, and further wherein pad bits are added to increase the number of bits to correspond to XN_{CBPS}, whenever the number of coded bits per symbol is less than N_{CBPS};
 permuting each group of coded bits and generating interleaved OFDM symbols in response thereto;
 grouping the interleaved OFDM symbols into blocks of N_{CBPS }bits; and
 permuting each block of N_{CBPS }bits associated with the interleaved OFDM symbols and generating interleaved OFDM tones in response thereto.
 According to yet another embodiment, a bit interleaver comprises
 a symbol interleaver operational to group the coded bits of a an OFDM symbol stream into blocks of XN_{CBPS }coded bits, wherein X is the desired number of OFDM symbols and further wherein N_{CBPS }is the number of coded bits per symbol, and further operational to permute each group of coded bits and generate interleaved OFDM symbols in response thereto only if the coded bits available for grouping correspond to no less than X OFDM symbols; and
 A tone interleaver operational to group the interleaved OFDM symbols into blocks of N_{CBPS }bits and permute each block of N_{CBPS }bits associated with the interleaved OFDM symbols and generate interleaved OFDM tones in response thereto.
 In cases where the number of bits is less than XN_{CBPS}, the symbol interleaver is skipped; and only a tone interleaving operation is performed. The foregoing symbol interleaving and tone interleaving operations can optionally be implemented with a single interleaving operation using a composite interleaver.
 According to still another embodiment, a composite bit interleaver is operational to group the coded bits of an OFDM symbol stream into blocks of XN_{CBPS }coded bits, wherein X is the desired number of OFDM symbols and further wherein N_{CBPS }is the number of coded bits per symbol, and further operational to permute each group of coded bits and generate interleaved OFDM symbols in response thereto only if the coded bits available for grouping correspond to no less than X OFDM symbols; and further operational to group the interleaved OFDM symbols into blocks of N_{CBPS }bits and permute each block of N_{CBPS }bits associated with the interleaved OFDM symbols and generate interleaved OFDM tones in response thereto.
 According to still another embodiment, a composite bit interleaver is operational to group the coded bits of an OFDM symbol stream into blocks of XN_{CBPS }coded bits, wherein X is the desired number of OFDM symbols, N_{CBPS }is the number of coded bits per symbol, and pad bits are used to increase the number of bits to correspond to X OFDM symbols whenever the number of coded bits per symbol is less than N_{CBPS}, and to permute each group of coded bits and generate interleaved OFDM symbols in response thereto; and further operational to group the interleaved OFDM symbols into blocks of N_{CBPS }bits and permute each block of N_{CBPS }bits associated with the interleaved OFDM symbols and generate interleaved OFDM tones in response thereto.
 According to still another embodiment, a bit interleaving method comprises the steps of
 permuting coded bits of an OFDM symbol stream and generating interleaved OFDM symbols to implement a desired interleaved OFDM symbol pattern in response thereto; and
 permuting each group of bits associated with each interleaved OFDM symbol and generating interleaved OFDM tones within each OFDM symbol in response to the desired interleaved OFDM symbol pattern.
 The foregoing step of permuting each group of bits associated with each interleaved OFDM symbol and generating interleaved OFDM tones within each OFDM symbol in response to the desired interleaved OFDM symbol pattern can be achieved via a plurality of different types of symbol/tone interleaving operations, for example, wherein each type of symbol/tone interleaving operation is determined via the desired interleaved OFDM symbol pattern. Thus, one could, for example, switch between two different types of interleavers every six OFDM symbols. In this instance, one embodiment of the symbol/tone interleaver could be employed for the first six OFDM symbols; while for the second six OFDM symbols, another (different) embodiment of the symbol/tone interleaver could be employed. The difference between the two interleaver structures could be as simple as doing a bit reversal between the two interleaver structures.
 According to still another embodiment, a bit interleaving method comprises the steps of
 permuting coded bits of an OFDM symbol stream and generating interleaved OFDM symbols in response thereto; and
 permuting each group of bits associated with each interleaved OFDM symbol and generating interleaved OFDM tones within each OFDM symbol in response thereto.
 ‘Pad bits’ can be used to increase the number of bits to correspond to XN_{CBPS }when the number of bits is less than XN_{CBPS}. The ‘pad bits’ can be added either at the input of the scrambler seen, for example, in
FIG. 2 , as a parallel stream to the input data, or at the input of the interleaver, for example, also seen inFIG. 2 , as a parallel stream coming from the puncturer output. Theoretically, the pad bits can be any random binary sequence. Using a random binary sequence is desirable, especially when the pad bits are introduced at the input of the interleaver. If, however, the pad bits are introduced at the input of the scrambler, an ‘all zero’ sequence or and ‘all one’ sequence is sufficient. The foregoing process is easily implemented and the scrambler would randomize these bits such that the pad bits at the output of the scrambler correspond to a random binary sequence.  Other aspects and features of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the invention becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 is a timedomain representation of timefrequency coding for multiband OFDM transmission; 
FIG. 2 is a simplified block diagram illustrating a typical transmitter architecture for a multiband OFDM system; 
FIG. 3 is a block diagram depicting a bit interleaving process according to one embodiment of the present invention; and 
FIGS. 4A and 4B illustrate symbol and tone interleaving processes implemented to generate coded bits that are interleaved across three symbols and within each symbol according to one embodiment of the present invention.  While the aboveidentified drawing figures set forth alternative embodiments, other embodiments of the present invention are also contemplated, as noted in the discussion. In all cases, this disclosure presents illustrated embodiments of the present invention by way of representation and not limitation. Numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention.
 The efficient bit interleaving scheme described herein below may be implemented for a UWB system employing multiband OFDM such as the one disclosed in U.S. patent application Ser. No. 10/688,169, entitled TimeFrequency Interleaved Orthogonal Frequency Division Multiplexing Ultra Wide Band Physical Layer, docket no. TI35949, filed on Oct. 18, 2003 by Anuj Batra et al. Patent application Ser. No. 10/688,169 is incorporated in its entirety by reference herein.
 In the foregoing UWB system, the OFDM symbols are coded across both time and frequency. An example of this timefrequency coding for multiband OFDM transmission is shown in
FIG. 1 . In this representation 10, the first OFDM symbol 12 is transmitted on channel number 1, the second OFDM symbol 14 is transmitted on channel number 3, the third OFDM symbol 16 is transmitted on channel number 2, and so on. The exact timefrequency coding pattern may be different from packet to packet and piconet to piconet. FromFIG. 1 , one can see that a guard interval 20 is inserted after each OFDM symbol. This guard interval 20 ensures the transmitter and receiver have sufficient time to switch from the current channel to the next channel.  One of the primary advantages of the multiband OFDM system is the capability to exploit the frequency diversity across the various subchannels. The design of the bit interleaving scheme is critical in exploiting the frequency diversity across the subchannels. One typical transmitter architecture 100 for a multiband OFDM system is illustrated in
FIG. 2 . The input bits are whitened using a scrambler 102, encoded using a convolutional code 104, interleaved 106, mapped onto an OFDM symbol 108, modulated into the appropriate subchannel 110, and transmitted.  In cases where the number of bits is less than XN_{CBPS}, (where X is a desired integer value), as stated herein before, the symbol interleaver is skipped; and only a tone interleaving operation is performed. The foregoing symbol interleaving and tone interleaving operations can easily be implemented with a single interleaving operation using a composite interleaver.
 Bit Interleaving
 The salient features and advantages of the bit interleaving scheme are described herein below. The UWB multipath channel is frequency selective and exhibits significant gain (or attenuation) variations across tone and subbands as stated herein before. This results in unequal error protection for the encoded bits transmitted across the various tone and subbands. The encoded bits of a multiband OFDM system are interleaved within each OFDM symbol and across OFDM symbols in accordance with the scheme described herein. The bit interleaving operation is performed in two stages: symbol interleaving followed by tone interleaving.
 In the first stage, the symbol interleaver permutes the encoded bits across OFDM symbols. The symbol interleaving provides the following advantages:

 1) enables the multiband OFDM system to obtain frequency diversity across the subbands. The average multipath energy in each subchannel (i.e. bandwidth 500 MHz) of typical UWB multipath channel impulse responses exhibits shadowing with a standard deviation of approximately 3 dB;
 2) randomizes the cochannel interference from simultaneously operating uncoordinated piconets. Depending on the timefrequency coding pattern that is employed, the cochannel interferer may be present in only a subset of the used subbands; and
 3) randomizes any generic narrowband interferers that are present within the UWB spectrum.
 In the second stage, the output bits of the symbol interleaver are passed onto a tone interleaver. The tone interleaver permutes the bits across the data tones within an OFDM symbol. The tone interleaving operation provides the following advantages:

 1) enables the multiband OFDM system to achieve frequency diversity across tones. The UWB channel impulse response is frequency selective and results in significant gain (or attenuation) variations across the OFDM tones. Typically, a null in the frequency domain, introduced by the multipath channel, affects a group of adjacent OFDM tones. The presence of a group of contiguous OFDM tones experiencing a poor SNR, due to the frequencydomain channel null, results in unequal error protection of the transmitted data bits and increases the performance degradation of the multiband OFDM system. Tone interleaving mitigates this problem by randomizing the distribution of the bits transmitted on tones experiencing a poor SNR; and
 2) randomizes the interference caused by generic narrowband interferers present within the frequency band of the OFDM symbol. The narrowband interferer affects a small set of contiguous tones and its impact on an OFDM system is analogous to that of burst errors in a singlecarrier system. Hence, tone interleaving mitigates the impact of narrowband interferer.
 The present invention is not so limited however; and it shall be understood that the symbol interleaving and tone interleaving operations can be implemented with a single stage interleaving operation using a composite interleaver.
 Mathematical Description
 A mathematic description of the symbol interleaving and tone interleaving operations are described herein below. For the sake of simplicity, a block interleaver structure has been considered for both the symbol and tone interleaver. Other interleaver structures such as random interleavers, random block interleavers, or triangular interleavers, can just as easily be chosen however, without loss of generality. Consider for example, a symbol interleaving operation among at most three consecutive OFDM symbols. This corresponds to a maximum interleaving latency of slightly less than 1 μs for a multiband OFDM system with a symbol duration of T_{SYMB}=312.5 ns.
 Let N_{CBPS}, for example, now be the number of coded bits per OFDM symbol. First, the coded bits are grouped together into blocks of 3N_{CBPS }coded bits, which corresponds to three OFDM symbols. Each group of coded bits is then permuted using a regular symbol block interleaver of size N_{CBPS}×3. Now let the sequences {U(i)} and {S(j)}, where i, j=0, . . . , 3N_{CBPS}−1, represent the input and output bits of the symbol block interleaver, respectively. The inputoutput relationship of this interleaver is then given by:
$S\left(j\right)=U\left\{\mathrm{Floor}\left(\frac{i}{{N}_{\mathrm{CBPS}}}\right)+3\text{\hspace{1em}}\mathrm{Mod}\left(i,{N}_{\mathrm{CBPS}}\right)\right\},$
where the function Floor(•) returns the largest integer value less than or equal to its argument value and where the function Mod(•) returns the remainder after division of N_{CBPS }by i. If the coded bits available at the input of the symbol block interleaver correspond to less than three OFDM symbols, then the symbol interleaving operation is not performed on these bits. This condition is expected to occur towards the end of the packet, when the number of coded bits available to the symbol block interleaver only corresponds to that of 1 or 2 OFDM symbols.  ‘Pad bits’ can be used to increase the number of bits to correspond to XN_{CBPS }when the number of bits is less than XN_{CBPS}. The ‘pad bits’ can be added either at the input of the scrambler 102, as a parallel stream 112 to the input data, or at the input of the interleaver 106, as a parallel stream 114 to the interleaver input data. Theoretically, the pad bits can be any random binary sequence. Using a random binary sequence is desirable, especially when the pad bits are introduced at the input of the interleaver 106. If, however, the pad bits are introduced at the input of the scrambler 102, an ‘all zero’ sequence or an ‘all one’ sequence is sufficient. The foregoing process is easily implemented; and the scrambler 102 would randomize these bits such that the pad bits at the output of the scrambler 102 correspond to a random binary sequence.
 The output of the symbol block interleaver is then passed through a tone block interleaver. In a multiband OFDM system, the number of coded bits per symbol (N_{CBPS}) can take a value of 50, 100 or 200 depending on the information data rate. The outputs of the symbol block interleaver in a typical example are grouped together into blocks of N_{CBPS }bits and then permuted using a regular block interleaver of size N_{Tint}×10, where N_{Tint}=N_{CBPS}/10. Now, let the sequences {S(i)} and {V(j)}, where i, j=0, . . . , N_{CBPS}−1, represent the input and output bits of the tone interleaver, respectively. The inputoutput relationship of the tone block interleaver is then given by:
$T\left(j\right)=S\left\{\mathrm{Floor}\left(\frac{i}{{N}_{T\text{\hspace{1em}}\mathrm{int}}}\right)+10\text{\hspace{1em}}\mathrm{Mod}\left(i,{N}_{T\text{\hspace{1em}}\mathrm{int}}\right)\right\},$
where the function Mod(•) returns the remainder after division of N_{Tint }by i.  Moving now to
FIG. 3 , one embodiment of a bit interleaving process 200 using the principles disclosed herein above is discussed in further detail herein below and can be seen to be implemented in three stages:  In the first stage 202, the coded bits, in the header or payload 203, that enter the scrambler 102 seen in
FIG. 2 , are grouped together into groups of XN_{CBPS }bits 204. These groups of XN_{CBPS }bits 204 are then passed through the convolutional encoder 104 and puncturer 116. After leaving the puncturer 116, each group of XN_{CBPS }bits 204 is interleaved in the second stage 205 using a block symbol interleaver 206. One embodiment of such a symbol interleaver is shown inFIG. 4A that depicts a XN_{CBPS}×3 block symbol interleaving process 300 for a data rate of 110 Mbps. Subsequent to the symbol interleaving process 300, the resultant bits generated via the symbol interleaving process 300 are interleaved in the third stage 207 using a block tone interleaver 208. One embodiment of such a tone interleaver is shown inFIG. 4B that depicts a (N_{CBPS}/10)×10 block tone interleaving process 400 for a data rate of 110 Mbps. The end results seen inFIG. 4B depict coded bits 410 that are interleaved across three symbols and within each symbol.  If there are less than XN_{CBPS }bits, depicted as <XN_{CBPS } 210 in
FIG. 3 , which can happen at the end of the header 203 or near the end of a packet, then the second stage 205 of the bit interleaving process 200 is skipped. Pad bits 112, 114 can however, be added as discussed herein before, as an input to the scrambler 102 or alternatively as an input to the interleaver 106. If the pad bits 112 are input to the scrambler 102, then every group of coded bits in the header or payload will be an integral multiple XN_{CBPS}, and <XN_{CBPS } 210 will never exist. In this instance, the second stage 205 will always be present. The pad bits 114 can also be input to the interleaver 106. In this way, coded bits <XN_{CBPS } 210 are increased until they equal XN_{CBPS }bits, and the second stage of bit interleaving 205 can again be implemented prior to tone interleaving.  The symbol and tone interleavers 205, 207, as stated herein before, can be timevarying, i.e., they can change at every time instant k. Thus, at one time instant k1, for example, a first combination of random interleavers, random block interleavers, or triangular interleavers may be employed to implement the symbol and/or tone interleavers 205, 207, while at a different time instant k2, a second combination of random interleavers, random block interleavers, or triangular interleavers may be employed to implement the symbol and/or tone interleavers 205, 207. The present invention is not so limited however, and although specific types of interleavers have been discussed herein before, those skilled in the art will readily appreciate that other interleaver types and combinations can just as easily be employed to implement a bit interleaver in accordance with the inventive principles set forth herein above.
 This invention has been described in considerable detail in order to provide those skilled in the multiband OFDM art with the information needed to apply the novel principles and to construct and use such specialized components as are required. In view of the foregoing descriptions, it should be apparent that the present invention represents a significant departure from the prior art in construction and operation. However, while particular embodiments of the present invention have been described herein in detail, it is to be understood that various alterations, modifications and substitutions can be made therein without departing in any way from the spirit and scope of the present invention, as defined in the claims which follow.
Claims (44)
153. (canceled)
54. A bit interleaving method comprising the steps of: permuting coded bits of an OFDM symbol stream and generating interleaved OFDM symbols in response thereto; and permuting each group of bits associated with each interleaved OFDM symbol and generating interleaved OFDM tones within each OFDM symbol in response thereto.
55. The bit interleaving method according to claim 54 , wherein generating interleaved OFDM symbols comprises interleaving OFDM symbols via an interleaver selected from the group consisting of a regular block interleaver, a random interleaver, a random block interleaver, a triangular interleaver, and a composite symbol/tone interleaver.
56. The bit interleaving method according to claim 54 , wherein generating interleaved OFDM tones comprises interleaving OFDM tones within each OFDM symbol via an interleaver selected from the group consisting of a regular block interleaver, a random interleaver, a random block interleaver, a triangular interleaver, and a composite symbol/tone interleaver.
57. The bit interleaving method according to claim 54 , wherein generating interleaved OFDM symbols comprises adding pad bits to the OFDM symbol stream sufficient to allow generating a desired number of OFDM symbols whenever the number of incoming OFDM symbol bits is insufficient to accommodate generating the desired number of OFDM symbols.
58. A bit interleaving method comprising:
permuting coded bits of an OFDM symbol stream and generating interleaved OFDM symbols to implement a desired interleaved OFDM symbol pattern in response thereto; and permuting each group of bits associated with each interleaved OFDM symbol and generating interleaved OFDM tones within each OFDM symbol in response to the desired interleaved OFDM symbol pattern.
59. The bit interleaving method according to claim 58 , wherein permuting each group of bits associated with each interleaved OFDM symbol and generating interleaved OFDM tones within each OFDM symbol in response to the desired interleaved OFDM symbol pattern is achieved via a plurality of different types of symbol/tone interleaving operations, wherein each type of symbol/tone interleaving operation is determined via the desired interleaved OFDM symbol pattern.
60. A bit interleaving method comprising:
grouping the coded bits of an OFDM symbol stream into blocks of 3N_{CBPS}, wherein 3 is a desired number of OFDM symbols and further wherein N_{CBPS }is the number of coded bits per symbol;
permuting each group of coded bits and generating interleaved OFDM symbols in response thereto only if the coded bits available for grouping correspond to no less than 3 OFDM symbols;
grouping the interleaved OFDM symbols into blocks of N_{CBPS }bits; and
permuting each block of N_{CBPS }bits associated with the interleaved OFDM symbols and generating interleaved OFDM tones in response thereto.
61. The bit interleaving method according to claim 60 , wherein N_{CBPS}=100.
62. The bit interleaving method according to claim 60 , wherein N_{CBPS}=200.
63. The bit interleaving method according to claim 60 , wherein the desired number of OFDM symbols is 6 and N_{CBPS}=200.
64. The bit interleaving method according to claim 60 , wherein permuting each group of coded bits and generating interleaved OFDM symbols in response thereto is implemented via a symbol interleaving operation having an inputoutput relationship defined by
wherein {U(i)} and {S(j)}, where i, j=0, . . . , XN_{CBPS}, represent the input and output bits of the symbol interleaving operation respectively, and further wherein the function Floor(.) returns the largest integer value less than or equal to its argument value, and further wherein the function Mod(•) returns the remainder after division of N_{CBPS }by i.
65. The bit interleaving method according to claim 64 , wherein N_{CBPS}=100.
66. The bit interleaving method according to claim 64 , wherein N_{CBPS}=200.
67. The bit interleaving method according to claim 69 , wherein the desired number of OFDM symbols is 6 and N_{CBPS}=200.
68. The bit interleaving method according to claim 60 , wherein permuting each block of N_{CBPS }its associated with the interleaved OFDM symbols and generating interleaved OFDM tones in response thereto comprises permuting each block of N_{CBPS }bits via a tone interleaving operation of size N_{Tint}×10, wherein N_{Tint}=N_{CBPS}10, and further wherein 10 is a desired integer value.
69. The bit interleaving method according to claim 68 , wherein and N_{Tint}=10.
70. The bit interleaving method according to claim 68 , wherein N_{Tint}=20.
71. The bit interleaving method according to claim 68 , wherein the tone interleaving operation has an inputoutput relationship defined by
wherein {S(i)} and {T(j)}, where i, j=0, . . . , N_{CBPS}−1 represent the input and output bits of the tone interleaving operation respectively, and further wherein the function Floor(•) returns the largest integer value no greater than it argument value, and further wherein the function Mod(•) returns the remainder after division of N_{Tint }by i.
72. The bit interleaving method according to claim 71 , wherein N_{Tint}=10.
73. The bit interleaving method according to claim 71 , wherein N_{Tint}=20.
74. A bit interleaving method comprising:
grouping the coded bits of an OFDM symbol stream into blocks of 3N_{CBPS}, wherein 3 is a desired number of OFDM symbols and further wherein N_{CBPS }the number of coded bits per symbol, and further wherein pad bits are added to increase the number of bits to correspond to 3N_{CBPS}, whenever the number of coded bits per symbol is less than N_{CBPS};
permuting each group of coded bits and generating interleaved OFDM symbols in response thereto;
grouping the interleaved OFDM symbols into blocks of N_{CBPS }bits; and
permuting each block of N_{CBPS }its associated with the interleaved OFDM symbols and generating interleaved OFDM tones in response thereto.
75. The bit interleaving method according to claim 74 , wherein N_{CBPS}=100.
76. The bit interleaving method according to claim 74 , wherein N_{CBPS}=200.
77. The bit interleaving method according to claim 74 , wherein the desired number of OFDM symbols 6 and N_{CBPS}=200.
78. The bit interleaving method according to claim 74 , wherein the step of permuting each group of coded bits and generating interleaved OFDM symbols in response thereto is implemented via a symbol interleaving operation having an inputoutput relationship defined by
wherein {S(i)} and {T(j)}, where i, j=0, . . . , 3N_{CBPS}, represent the input and output bits of the symbol interleaving operation respectively, and further wherein the function Floor(•) returns the largest integer value less than or equal to its argument value, and further wherein the function Mod(•) returns the remainder after division of N_{CBPS }by i.
79. The bit interleaving method according to claim 74 , wherein permuting each block of N_{CBPS }bits associated with the interleaved OFDM symbols and generating interleaved OFDM tones in response thereto comprises permuting each block of N_{CBPS }bits via a tone interleaving operation of size N_{Tint}×10, wherein N_{Tint}=t N_{CBPS}/10, and further wherein 10 is a desired integer value.
80. The bit interleaving method according to claim 79 , wherein desired number of OFDM symbols is 6.
81. The bit interleaving method according to claim 78 , wherein the tone interleaving operation has an inputoutput relationship defined by
wherein {S(i)} and {T(j)}, where i, j=0, . . . , N_{CBPS}−1 represent the input and output bits of the tone interleaving operation respectively, and further wherein the function Floor(•) returns the largest integer value no greater than it argument value, and further wherein the function Mod(•) returns the remainder after division of N_{Tint }by i.
82. The bit interleaving method according to claim 68 , wherein and N_{Tint}=10.
83. The bit interleaving method according to claim 68 , wherein N_{Tint}=20.
84. A bit interleaver comprising:
a symbol interleaver operational to group the coded bits of a an OFDM symbol stream into blocks of 1200 coded bits, wherein 6 is the desired number of OFDM symbols and further wherein 200 is the number of coded bits per symbol, and further operational to permute each group of coded bits and generate interleaved OFDM symbols in response thereto only if the coded bits available for grouping correspond to no less than 6 OFDM symbols; and
a tone interleaver operational to group the interleaved OFDM symbols into blocks of 200 bits and permute each block of 200 bits associated with the interleaved OFDM symbols and generate interleaved OFDM tones in response thereto.
85. The bit interleaver according to claim 84 , wherein the symbol interleaver is configured to have an inputoutput relationship defined by
wherein {S(i)} and {T(j)}, where i, j=0, . . . , 1199, represent the input and output bits of the symbol interleaver respectively, and further wherein the function Floor(•) returns the largest integer value less than or equal to its argument value, and further wherein the function Mod(•) returns the remainder after division of 200 by i.
86. The bit interleaver according to claim 84 , wherein the tone interleaver is configured to have an inputoutput relationship defined by
wherein {S(i)} and {T(j)}, where i, j=0, . . . , 199 represent the input and output bits of the tone interleaver respectively, and further wherein the tone interleaver size=N_{Tint}×10, N_{Tint}=20 and 10 is a desired integer value, and further wherein the function Floor(•) returns the largest integer value no greater than it argument value, and further wherein the function Mod(•) returns the remainder after division of N_{Tint }By i.
87. The bit interleaving method according to claim 71 , wherein N_{Tint}=10.
88. The bit interleaving method according to claim 71 , wherein N_{Tint}=20.
89. A composite bit interleaver operational to group the coded bits of an OFDM symbol stream into blocks of 1200 coded bits, wherein 6 is the desired number of OFDM symbols and further wherein 200 is the number of coded bits per symbol, and further operational to permute each group of coded bits and generate interleaved OFDM symbols in response thereto only if the coded bits available for grouping correspond to no less than 6 OFDM symbols; and further operational to group the interleaved OFDM symbols into blocks of 200 its and permute each block of 200 bits associated with the interleaved OFDM symbols and generate interleaved OFDM tones in response thereto.
90. The composite bit interleaver according to claim 89 , wherein the symbol interleaving operation is defined via an inputoutput relationship according to
wherein {S(i)} and {T(j)}, where i, j=0, . . . , 1199, represent the input and output bits of the symbol interleaving operation respectively, and further wherein the function Floor(•) returns the largest integer value less than or equal to its argument value, and further wherein the function Mod(•) returns the remainder after division of 200 by i.
91. The composite bit interleaver according to claim 89 , wherein the tone interleaving operation is defined via an inputoutput relationship according to
wherein {S(i)} and {T(j)}, where i, j=0, . . . , 199 represent the input and output bits of the tone interleaving operation respectively, and further wherein the tone interleaver size=N_{Tint}×10, N_{Tint}=20 and 10 is a desired integer value, and further wherein the function Floor(•) returns the largest integer value no greater than it argument value, and further wherein the function Mod(•) returns the remainder after division of N_{Tint }by i.
91. A composite bit interleaver operational to group the coded bits of an OFDM symbol stream into blocks of 1200 coded bits, wherein 6 is the desired number of OFDM symbols, N_{CBPS }is the number of coded bits per symbol, and pad bits are used to increase the number of bits to correspond to 6 OFDM symbols whenever the number of coded bits per symbol is less than N_{CBPS}, and to permute each group of coded bits and generate interleaved OFDM symbols in response thereto; and further operational to group the interleaved OFDM symbols into blocks of 200 bits and permute each block of 200 bits associated with the interleaved OFDM symbols and generate interleaved OFDM tones in response thereto.
92. The composite bit interleaver according to claim 91 , wherein the symbol interleaving operation is defined via an inputoutput relationship according to
wherein {S(i)} and {T(j)}, where i, j=0, . . . , 1199, represent the input and output bits of the symbol interleaving operation respectively, and further wherein the function Floor(•) returns the largest integer value less than or equal to its argument value, and further wherein the function Mod(•) returns the remainder after division of 200 by i.
93. The composite bit interleaver according to claim 91 , wherein the tone interleaving operation is defined via an inputoutput relationship according to
wherein {S(i)} and {T(j)}, where i, j=0, . . . , N_{CBPS}−1 represent the input and output bits of the tone interleaving operation respectively, and further wherein the tone interleaver size=N_{Tint}×A, N_{Tint}=20 and 10 is a desired integer value, and further wherein the function Floor(•) returns the largest integer value no greater than it argument value, and further wherein the function Mod(•) returns the remainder after division of N_{Tint }by i.
94. The bit interleaving method according to claim 93 , wherein N_{Tint}=10.
95. The bit interleaving method according to claim 93 , wherein N_{Tint}=20.
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