Patent Publication Number: US-2010111145-A1

Title: Baseband unit having bit repetitive encoded/decoding

Description:
This patent application is claiming priority under 35 USC §119 to a provisionally filed patent application entitled 60 GHz SINGLE CARRIER MODULATION, having a provisional filing date of Nov. 5, 2008, and a provisional Ser. No. 61/111,685. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     NOT APPLICABLE 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     NOT APPLICABLE 
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     This invention relates generally to wireless communication systems and more particularly to wireless communication devices that operate in such systems. 
     2. Description of Related Art 
     Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), radio frequency identification (RFID), Enhanced Data rates for GSM Evolution (EDGE), General Packet Radio Service (GPRS), and/or variations thereof. 
     Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, RFID reader, RFID tag, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system or a particular RF frequency for some systems) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network. 
     For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the receiver is coupled to an antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies then. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard. 
     As is also known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna. 
     While transmitters generally include a data modulation stage, one or more IF stages, and a power amplifier, the particular implementation of these elements is dependent upon the data modulation scheme of the standard being supported by the transceiver. For example, if the baseband modulation scheme is Gaussian Minimum Shift Keying (GMSK), the data modulation stage functions to convert digital words into quadrature modulation symbols, which have a constant amplitude and varying phases. The IF stage includes a phase locked loop (PLL) that generates an oscillation at a desired RF frequency, which is modulated based on the varying phasesproduced by the data modulation stage. The phase modulated RF signal is then amplified by the power amplifier in accordance with a transmit power level setting to produce a phase modulated RF signal. 
     As another example, if the data modulation scheme is 8-PSK (phase shift keying), the data modulation stage functions to convert digital words into symbols having varying amplitudes and varying phases. The IF stage includes a phase locked loop (PLL) that generates an oscillation at a desired RF frequency, which is modulated based on the varying phasesproduced by the data modulation stage. The phase modulated RF signal is then amplified by the power amplifier in accordance with the varying amplitudes to produce a phase and amplitude modulated RF signal. 
     As the desire for wireless communication devices to support multiple standards continues, recent trends include the desire to integrate more functions on to a single chip. For instance, as standards develop for the 60 GHz frequency band (e.g., 57 GHz to 66 GHz), it is desired to have communication devices be able to function in the 60 GHz frequency band as well as other standards (e.g., IEEE 802.11, GSM, CDMA, etc.) in different frequency bands (e.g., 900 MHz, 1800 MHz, 1900 MHz, 2100 MHz, 2.4 GHz, 5 GHz, 29 GHz, etc.). 
     When operating in the 60 GHz frequency band, it is desirable to operate at very high speeds (e.g., greater than 1 Giga-bit-per-second). However, there are times when a device will not be able at such data rates and have to use a “fall-back” data rate (e.g., 375 Mbps). In these instances, repeating data bits is useful to improve the reliability of data transmissions, but can introduce spectral lines or tones into the transmitting and, hence, the received signal. Such spectral lines or tones reduce the reception quality thereby making such solutions less than optimal. 
     Therefore, a need exists for a wireless communication device that at least partially overcomes one or more of the wireless communication device issues discussed above. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to apparatus and methods of operation that are further described in the following Brief Description of the Drawings, the Detailed Description of the Invention, and the claims. Other features and advantages of the present invention will become apparent from the following detailed description of the invention made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is a schematic block diagram of an embodiment of a millimeter wave network in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic block diagram of an embodiment of a baseband processing module in accordance with an embodiment of the present invention; 
         FIG. 3  is a schematic block diagram of another embodiment of a baseband processing module in accordance with an embodiment of the present invention; 
         FIG. 4  is a diagram of an example of a data block in accordance with an embodiment of the present invention; 
         FIG. 5  is a diagram of an example of bit repetition processing in accordance with an embodiment of the present invention; 
         FIG. 6  is a diagram of another example of bit repetition processing in accordance with an embodiment of the present invention; and 
         FIG. 7  is a logic diagram of an embodiment of a method for bit repetition processing in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic block diagram of an embodiment of a millimeter wave network that includes a plurality of wireless communication devices  10 - 12 . The wireless communication devices  10 - 12  may be a personal computer, laptop computer, personal entertainment device, cellular telephone, personal digital assistant, a game console, a game controller, and/or any other type of device that communicates real-time and/or non-real-time signals via a wireless connection. Each of the wireless communication devices  10 - 12  includes a millimeter wave (MMW) transceiver  16  and a baseband unit  14 . The MMW transceiver  16  includes at least one receiver section and at least one transmitter section that allow the device to support one or more standards (e.g., GSM, IEEE 802.11, WCDMA, 60 GHz, etc.) in one or more frequency bands. 
     The baseband unit  14  includes a processing module  48  and one or more input/output (I/O) interface modules (e.g., one or more of integrated circuit (IC) pins, general purpose input/output (GPIO), buffers, drivers, wires, IC traces, etc.). The processing module may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module may have an associated memory and/or memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of the processing module. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that when the processing module implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Further note that, the memory element stores, and the processing module executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in  FIGS. 1-7 . 
     In operation, the receiver section of the MMW transceiver is operable to amplify an inbound MMW signal (e.g., carrier frequency in the rage of 3 GHz to 300 GHz) to produce an amplified inbound MMW signal. The receiver section may then mix in-phase (I) and quadrature (Q) components of the amplified inbound MMW signal with in-phase and quadrature components of a local oscillation to produce a mixed I signal and a mixed Q signal. The mixed I and Q signals are combined to produce an inbound symbol stream. In this embodiment, the inbound symbol may include phase information (e.g., +/−Δθ[phase shift] and/or θ(t) [phase modulation]) and/or frequency information (e.g., +/−Δf [frequency shift] and/or f(t) [frequency modulation]). In another embodiment and/or in furtherance of the preceding embodiment, the inbound RF signal includes amplitude information (e.g., +/−ΔA [amplitude shift] and/or A(t) [amplitude modulation]). To recover the amplitude information as part of the inbound symbol stream, the receiver section includes an amplitude detector such as an envelope detector, a low pass filter, etc. The baseband unit  14  converts the inbound symbol stream into inbound data as will be discussed in greater detail with reference to  FIGS. 2-7 . 
     The baseband unit  14  is further operable to convert outbound data (e.g., voice, audio, video, text, graphics, etc.) into an outbound symbol stream as will be discussed in greater detail with reference to  FIGS. 2-7 . The transmitter section of the MMW transceiver converts the outbound symbol stream into an outbound MMW signal. This may be done in a variety of ways. For example, the transmitter section may mix the outbound symbol stream with a local oscillation to produce an up-converted signal. One or more power amplifiers and/or power amplifier drivers amplifies the up-converted signal, which may be MMW bandpass filtered, to produce the outbound MMW signal. In another embodiment, the transmitter section includes an oscillator that produces an oscillation. The outbound symbol stream provides phase information (e.g., +/−Δθ[phase shift] and/or θ(t) [phase modulation]) that adjusts the phase of the oscillation to produce a phase adjusted MMW signal, which is transmitted as the outbound MMW signal. In another embodiment, the outbound symbol stream includes amplitude information (e.g., A(t) [amplitude modulation]), which is used to adjust the amplitude of the phase adjusted MMW signal to produce the outbound MMW signal. 
     In yet another embodiment, the transmitter section includes an oscillator that produces an oscillation. The outbound symbol provides frequency information (e.g., +/−Δf [frequency shift] and/or f(t) [frequency modulation]) that adjusts the frequency of the oscillation to produce a frequency adjusted MMW signal, which is transmitted as the outbound MMW signal. In another embodiment, the outbound symbol stream includes amplitude information, which is used to adjust the amplitude of the frequency adjusted MMW signal to produce the outbound MMW signal. In a further embodiment, the transmitter section includes an oscillator that produces an oscillation. The outbound symbol provides amplitude information (e.g., +/−ΔA [amplitude shift] and/or A(t) [amplitude modulation) that adjusts the amplitude of the oscillation to produce the outbound MMW signal. 
     The conveyance of a MMW signal from one wireless communication device to the other is done in accordance with a particular standardized protocol, which describes a frame format. In addition, a communication typically includes a detection period and a clear channel period (CE). In the example of the  FIG. 1 , a frame includes one or more header sections and one or more data fields (which includes one or more guard intervals and one or more data blocks). Note that a frame may be transmitted in one or more data bursts. 
     The particular protocol generally dictates the format of the header. For example, the header may be contained in one of the single carrier modulation (SCM) blocks that includes 448 symbols. It may be formatted in a shortened r=½ code (LDPC (448,112)) with factor-of-2 outer repetition code and include 56 bits of information. In addition, the header may be scrambled from bit  7  forward and/or have the scrambler restarted at the start of the data. 
     The header section may include the following fields: 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                   
                 Number 
                 Start 
                   
               
               
                 Field Name 
                 of bits 
                 Bit 
                 Description 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Scrambler 
                 7 
                 0 
                 bits X1-X7 of the initial scrambler state. 
               
               
                 Initialization 
               
               
                 MCS 
                 8 
                 7 
                 Index into the Modulation and Coding 
               
               
                   
                   
                   
                 Scheme table 
               
               
                 Additional 
                 1 
                 15 
                 A value of 1 Indicates that this PDDU is 
               
               
                 PPDU 
                   
                   
                 immediately followed by another PPDU 
               
               
                   
                   
                   
                 with no IFS or preamble on the subsequent 
               
               
                   
                   
                   
                 PPDU. A value of 0 indicates that no 
               
               
                   
                   
                   
                 additional PPDU follows this PPDU. 
               
               
                 Length 
                 18 
                 16 
                 Number of data octets in the PSDU. 
               
               
                   
                   
                   
                 Range 0-262143 
               
               
                 Reserved 
                 6 
                 34 
                 Set to 0, ignored by receiver 
               
               
                 HCS 
                 16 
                 40 
                 Header check sequence 
               
               
                   
               
            
           
         
       
     
     The scrambler initialization includes 7 bits that set the initial state of the scrambler shift register. In an embodiment, the bits should be as random as possible on every transmission of a burst. Note that both the header and the data field (e.g., PSDU) are scrambled by the same sequence and that the scrambler may be reset again to the scrambler seed at the start of the PSDU and also at the start of the header repetition if the MCS is 0. 
       FIG. 2  is a schematic block diagram of an embodiment of a baseband unit  14  that includes a processing module  48  and one or more input/output modules (I/O). The processing module  48  supports a transmit baseband section and a receive baseband section. The transmit baseband section includes a scramble module  20 , a bit repetition process module  22 , an encoder  24  (e.g., low density parity check (LDPC)), a binary and/or quadrature phase shift keying (B/QPSK) module  26 , a phase rotation module  28  (e.g., π/2), a filter  30  (e.g., low pass and/or bandpass filter), and a modulator  32  (e.g., base band to low intermediate frequency (IF)). The receive baseband section includes a demodulator  34  (e.g., low IF to baseband), a filter  36  (e.g., low pass and/or bandpass), a phase rotation decoding module  38  (e.g., π/2), B/QPSK demapping module  40 , a decoding module  42  (e.g., LDPC), a bit repetition decoding module  44 , and a de-scramble module  46 . 
     For outbound data, the scramble module scrambles an outbound data word (e.g., 168 bits) to produce a scramble data word. The bit repetition module repeats the bits of the scrambled data word, processes the repeated bits to produce a random sequence of repeated bits, and appends the random sequence of repeated bits to the scrambled data word to produce a repeated data word (e.g., 336 bits). In this regard, the bit repetition module is adding redundancy to the data to improve data transmission integrity and substantially avoids injection of spectral lines or tones via the processing to produce the random sequence. For example, the repeated bits may be exclusively ORed with a pseudo random sequence at a known initialization point to produce the random sequence. Examples of this are provided in  FIGS. 5 and 6 . 
     The LDPC encoding module encodes the repeated data word to produce an LDPC encoded data word (e.g., 672 bits). The B/QPSK mapping module maps bits of the encoded data word to a binary constellation (e.g., +1 or −1) or a quadrature constellation (e.g., +1, −1, +i, or −i). The π/2 rotation module rotates each mapped symbol outputted by the B/QPSK mapping module by π/2 to produce rotated symbols. The filter (e.g., LPF or BPF) filters the rotated symbols to produce filtered symbols. The modulator modulates the filtered symbols to convert the outbound symbol stream from a baseband signal to a low intermediate frequency signal. Alternatively, the modulator may be omitted, and the baseband outbound symbol stream may be provided directly to the transmitter section of the MMW transceiver. 
     The receiver side of the processing module essentially performs the inverse of the corresponding components of the transmitter side. In particular, the demodulator demodulates a low inbound IF symbol stream to produce a baseband inbound symbol stream. The filter filters the inbound symbol stream, which is decoded via the π/2 rotation decoding module to produce inbound mapped symbols. The B/QPSK demapping module demaps the inbound mapped symbols to recover the repeated data word. The LDPC decoding module decodes the repeated data word to recover the repeated data word. 
     The bit repetition decoding module, utilizing the known random sequence used by the bit repetition encoding module, decodes the repeated data word to recover the scrambled data word. The de-scramble module descrambles the scrambled data word to produce the inbound data. 
       FIG. 3  is a schematic block diagram of another embodiment of a baseband unit  14  that includes the processing module  48  and one or more IO interface modules. The processing module  48  supports a transmit baseband section and a receive baseband section. The transmit baseband section includes a scramble module  20 , a bit repetition process module  22 , an encoder  24 , and a minimum shift keying (MSK) or Gaussian (GMSK) modulator  50 . The receive baseband section includes a G/MSK demodulator  52 , a decoding module  42 , a bit repetition decoding module  44 , and a de-scramble module  46 . 
     For outbound data, the scramble module scrambles an outbound data word (e.g., 168 bits) to produce a scramble data word. The bit repetition module repeats the bits of the scrambled data word, processes the repeated bits to produce a random sequence of repeated bits, and appends the random sequence of repeated bits to the scrambled data word to produce a repeated data word (e.g., 336 bits). In this regard, the bit repetition module is adding redundancy to the data to improve data transmission integrity and substantially avoids injection of spectral lines or tones via the processing to produce the random sequence. For example, the repeated bits may be exclusively ORed with a pseudo random sequence at a known initialization point to produce the random sequence. Examples of this are provided in  FIGS. 5 and 6 . 
     The LDPC encoding module encodes the repeated data word to produce an LDPC encoded data word (e.g., 672 bits). The MSK modulator modulates the output of the summing module to produce the outbound symbol stream. 
     The receiver side of the processing module essentially performs the inverse of the corresponding components of the transmitter side. In particular, the G/MSK demodulator demodulates an inbound symbol stream. The LDPC decoding module decodes the output of the MSK demodulator to recover the repeated data word. 
     The bit repetition decoding module, utilizing the known random sequence used by the bit repetition encoding module, decodes the repeated data word to recover the scrambled data word. The de-scramble module descrambles the scrambled data word to produce the inbound data. In this embodiment, the GMSK modulation, which is a constant envelop modulation, approximates the π/2 rotation and B/QPSK functions. 
       FIG. 4  is a diagram of an example of a data field of a frame that includes one or more guard intervals (GI) and one or more data blocks. In this example, each GI may include 64 symbols and each data block may include 448 symbols. In this instance, two 672-bit LDPC codewords fit into 3 blocks of data for π/2-BPSK such that shortening is only performed at end of a frame using rules similar to the OFDM spec. Alternatively, four 672-bit LDPC codewords fit into 3 blocks of data for π/2-QPSK. In either instance, the guard interval may be a fixed L=64 Golay sequence instead of a cyclic prefix, though blocks may still have a cyclic property if the GI of the next symbol is included. 
       FIG. 5  is a diagram of an example of bit repetition processing of a data word that includes a number of bits (e.g., 168 bits outputted of a scrambler in the baseband receive path) as performed by the bit repetition module  22 . The bit repetition process repeats the bits (b k ) and exclusive ORs them with a pseudo random sequence (c k ) to produce the repeated bits (β k ). The bit repetition module appends the repeated bits on the original bits to produce the repeated data word of 336 bits. 
     On the receive side, the bit repetition decoding module  44  receives a repeated data word, exclusive ORs it with the pseudo random sequence (ck) to recover the repeated bits. From the original bits b k  and the repeated bits, the bit repetition decoding module recovers the scrambled data word. 
       FIG. 6  is a diagram of another example of bit repetition processing where the data word includes less than the number of bits (e.g., 168 bits or another number), which may occur at the end of a frame. In this instance, the bit repetition module determines that the received data word includes less than 168 bits (or some other size). The bit repetition module adds padding data (p k ) to the bits of the data word (b k ) to provide a word of 168 bits. The bit repetition module functions as previously described to produce the repeated data word that includes repeated bits of the desired data (β k ) and repeated bits of the padded data (πk). 
     On the receive side, the bit repetition module recovers the original bits and the padding bits as previously discussed. The bit repetition module then determines the padding bits and removes them such the only the bits of interest are left. 
       FIG. 7  is a logic diagram of an embodiment of a method for bit repetition processing. The method begins at step  60  where the processing module determines parameters of the data block (e.g., maximum size, number of bits, etc.). The method continues at step  62  where the processing module determines whether padding is needed (e.g., is the current data block is the last of a frame and includes less than a maximum of bits). If not, the method continues at step  64  where the processing module repeats the bits as previously discussed with reference to  FIG. 5 . 
     When padding is needed, the method continues at step  66  where the processing module performs one or more padding equations. Such padding equations include 
     
       
         
           
             
               N 
               CW 
             
             = 
             
               ⌈ 
               
                 
                   Length 
                   · 
                   8 
                 
                 
                   
                     L 
                     CW 
                   
                   · 
                   R 
                 
               
               ⌉ 
             
           
         
       
       
         
           
             
               N 
               DATA_PAD 
             
             = 
             
               
                 
                   N 
                   CW 
                 
                 · 
                 
                   L 
                   CW 
                 
                 · 
                 R 
               
               - 
               
                 Length 
                 · 
                 8 
               
             
           
         
       
       
         
           
             
               N 
               BLKS 
             
             = 
             
               ⌈ 
               
                 
                   
                     N 
                     CW 
                   
                   · 
                   
                     L 
                     CW 
                   
                 
                 
                   N 
                   CBPB 
                 
               
               ⌉ 
             
           
         
       
       
         
           
             
               N 
               BLK_PAD 
             
             = 
             
               
                 
                   N 
                   BLKS 
                 
                 · 
                 
                   N 
                   CBPB 
                 
               
               - 
               
                 
                   N 
                   CW 
                 
                 · 
                 
                   L 
                   CW 
                 
               
             
           
         
       
     
     where:
         R=code rate, Length=number of input data bytes (or total replicated data bytes for MCS 0)   L CW =length of code word (672 bits), N CW =# codewords   N DBPB =# data (information) bits per block, N CBPB =# coded bits per block=N DBPB /R   N DATA     —     PAD =# data pad bits   N BLKS =# blocks of SC symbols   N BLK     —     PAD =# of block pad bits.       

     The method then continues at steps  68  and  70  where the processing module adds the padding bits and repeats the bits are previously described with reference to  FIG. 6 . 
     As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “coupled to” and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “operable to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item. As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal  1  has a greater magnitude than signal  2 , a favorable comparison may be achieved when the magnitude of signal  1  is greater than that of signal  2  or when the magnitude of signal  2  is less than that of signal  1 . 
     The present invention has also been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claimed invention. 
     The present invention has been described above with the aid of functional building blocks illustrating the performance of certain significant functions. The boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality. To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claimed invention. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.