Abstract:
The present invention, illustrated in various embodiments, provides mechanisms for transferring data in wireless communications systems. In one exemplary embodiment, the data is transferred in an access point (AP) used in a wireless local area network (WLAN), which comprises a wireless communication system connected to a local area network (LAN). The access point includes a baseband chip capable of adapting various radio frequency (RF) units. Each RF unit in turns includes a plurality of RF sub units connected in a daisy-chain manner. Each RF sub unit is also connected to at least one antenna. The access point thus includes a number of antennas that, together with the RF units and the baseband chip, form a smart antenna. In a receiving mode, the data received from the smart antenna travels through the RF sub units in each RF unit, and the data from the RF units travels to the baseband chip. Conversely, in a transmitting mode, the data transmitted from the baseband chip travels to the RF units, and in each RF unit the data travels through the sub units to the smart antenna. In one embodiment, each RF sub unit is removably connected to another RF sub unit, and each RF unit is removably connected to the baseband chip, which allows flexibility in selecting a system configuration with an appropriate number of antennas for the smart antenna.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to wireless communication systems, and more specifically to transferring data in such systems.  
         BACKGROUND OF THE INVENTION  
         [0002]    Antennas are commonly used in wireless communication systems in which the antennas radiate power for signals to be received and transmitted through the antennas to appropriate signal transmitters and receivers. Adaptive antenna refers to an array of antennas capable of dynamically changing its antenna pattern to adjust to noise, interference, and different paths of users using the antenna, etc. Adaptive antennas form beams for transmission and enhance signals because they can adjust their patterns to track mobile users. Switched beam technologies use a number of beams at an antenna site for the receiver to select the beam that provides the best signals. Smart-antenna systems usually include both adaptive antennas and switched beam technologies. The number of antennas in an array for use in adaptive antennas and/or smart antennas varies depending on the applications using the antennas, the distance between the wireless transmitters and receivers, whether the system processing the wireless signals are powerful or not, etc. However, in general, the more antennas are used in a system, the better it is for the system&#39;s reception and transmission performance. Unfortunately, as the number of antennas increases, transferring the data through the antennas becomes more difficult and expensive because adding antennas to a system results in additional components and costs to the system. For example, in various cases, additional radio-frequency (RF) data paths must be added, and, as the number of these paths increases, the interface between the paths and the baseband chip becomes more complicated. Additionally, various current approaches do not provide the flexibility in choosing and/or adjusting the number of antennas as desired. Once a number of antennas are designed for a system, the system is fixed with that number of antennas. Consequently, there is a need to provide mechanisms to solve the above problems and associated issues.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention, illustrated in various embodiments, provides mechanisms for transferring data in wireless communications systems. In one exemplary embodiment, the data is transferred in an access point (AP) used in a wireless local area network (WLAN), which comprises a wireless communication system connected to a local area network (LAN). The access point includes a baseband chip capable of adapting various radio frequency (RF) units. Each RF unit in turns includes a plurality of RF sub units connected as a daisy chain. Each RF sub unit is also connected to at least one antenna. The access point thus includes a number of antennas that, together with the RF units and the baseband chip, form a smart antenna.  
           [0004]    In a receiving mode, the data received from the smart antenna travels through the RF sub units in each RF unit, and the data from the RF units travels to the baseband chip. Conversely, in a transmitting mode, the data transmitted from the baseband chip travels to the RF units, and in each RF unit the data travels through the sub units to the smart antenna.  
           [0005]    In one embodiment, each RF sub unit is removably connected to another RF sub unit, and each RF unit is removably connected to the baseband chip, which allows flexibility in selecting a system configuration with an appropriate number of antennas for the smart antenna.  
       
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS  
       [0006]    [0006]FIG. 1 shows a wireless communication system upon which embodiments of the invention may be implemented;  
         [0007]    [0007]FIG. 2A shows an access point in accordance with one embodiment;  
         [0008]    [0008]FIG. 2B illustrates a mechanism in which one connecting point between an RF unit and the baseband unit may be used for both a receiving mode and a transmitting mode;  
         [0009]    [0009]FIG. 3 shows a RF unit in accordance with one embodiment;  
         [0010]    [0010]FIG. 4 shows the data traveling through four exemplary RF sub units, in accordance with one embodiment;  
         [0011]    [0011]FIG. 5 shows a RF sub unit in accordance with one embodiment;  
         [0012]    [0012]FIG. 6 shows a receiving unit in accordance with one embodiment;  
         [0013]    [0013]FIG. 7A shows a first type of an interleaver in accordance with one embodiment;  
         [0014]    [0014]FIG. 7B shows a second type of an interleaver in accordance with one embodiment;  
         [0015]    [0015]FIG. 8 shows a transmitting unit in accordance with one embodiment;  
         [0016]    [0016]FIG. 9A shows a first type of a de-interleaver in accordance with one embodiment;  
         [0017]    [0017]FIG. 9B shows a second type of a de-interleave in accordance with one embodiment; and  
         [0018]    [0018]FIG. 10 shows a baseband unit in accordance with one embodiment.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     System Overview  
       [0019]    [0019]FIG. 1 shows a wireless communication system  100  upon which embodiments of the invention may be implemented. Exemplary technologies used in system  100  include the code-division multiple access (CDMA), the time-division multiple access (TDMA), the global system for mobile communications (GSM), etc. System  100  includes an access point  125  and a plurality of stations  130 - 1 ,  130 - 2 , . . . ,  130 -N. Access point  125  includes an access station  110  connected to a smart antenna  120 . In one embodiment, access point  125  is connected to an electronic network (not shown), which transmits information through access station  110 , smart antenna  120 , and wirelessly to stations  130 . Similarly, the network wirelessly receives information from stations  130  through smart antenna  120  and access station  110 , etc. Generally, access station  110  processes signals received or sent through antenna  120 . To improve reception and transmission performance of a particular station  130 , access point  125  allows signal beams radiating through antenna  120  to be focused to that station  130 .  
         [0020]    In one embodiment, a local area network (LAN) is used as the network in the above discussion. However, the invention is not limited to LANs, other networks are within the scope of the invention, including, for example, the digital subscriber line (DSL), the Ethernet, the cable modem, etc. LAN is a computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings  
         [0021]    Normally, a station  130  is a mobile device wirelessly communicating with the network through access point  125 . Examples of a station  130  include a laptop or a desktop computer, a personal digital assistance (PDA), a cellular phone, etc. Each station  130  includes at least one antenna and a processing unit processing signals to communicate wirelessly with access point  125 . The processing unit may be different from access station  110 , but, in general, perform the same function as access station  110 . Even though stations  130  are moveable from one position to another position, to communicate effectively with access point  125 , a station  130  must be within the coverage range of access point  125 . This coverage range varies depending on various factors including the transmitting frequency, the number of antennas in smart antenna  120  or in stations  130 , the power of each antenna, the processing power of access station  110  and of the processing unit in stations  130 , etc. In general, a lower-frequency system has a wider range of coverage than a higher-frequency system. For example, a system with the IEEE 802.11b or 802.11g protocol has a coverage area four times greater than that of the 802.11a protocol because the 802.11b and 802.11g protocol operates at a 2.4 Ghz frequency, which is much slower than the 5.0 Ghz frequency of the 802.11a protocol. Those skilled in the art will recognize that IEEE stands for the “Institute of Electrical and Electronics Engineers.” 
       The Access Point  
       [0022]    [0022]FIG. 2A shows access point  125  having a plurality of RF units  220 ( 1 ) to  220 (M) connected to a baseband unit or baseband chip  210  at lines  2300 ( 1 ) to  2300 (M), respectively, in accordance with one embodiment. A RF unit  220  includes a plurality of RF sub units  2200  (not shown), each of which carries at least one antenna. The antennas of all RF sub units  2200 , together with RF sub units  2200  and baseband chip  210 , function as smart antenna  120 .  
         [0023]    In the receiving mode, RF units  220  process the analog radio frequency signals received from smart antenna  120 , down-convert the radio frequency to the intermediate frequency, combine and digitize the signals, etc. In the same receiving mode, baseband chip  210  demodulates the digitized signals received from RF units  220 , converts them to the digital domain of zeros and ones, and sends them to the LAN, etc. In the transmitting mode, baseband chip  210  receives the digital data from the LAN, modulates the data, and sends it to RF units  220 . RF units  220 , upon receiving the digital data, convert it to analog, up-convert the data&#39;s intermediate frequency to the radio frequency, and send the data to smart antenna  120 , which transmits the data over the air.  
         [0024]    In one embodiment, each RF unit  220  is removably connected to baseband chip  210 . That is, each unit  220  is easily removed from or attached to baseband chip  210 , which can be done by any convenient mechanism. In embodiments where printed-circuit boards (PCBs) are used to implement units  220  and baseband chip  210 , any mechanism for connecting PCBs is effective.  
         [0025]    In embodiments that allow either receiving or transmitting the data at a time, such as in the LAN situation, each RF unit  220  uses only one connecting point at line  2300  for both receiving and transmitting. In embodiments that allow both receiving and transmitting at the same time, each RF unit  220  uses one connecting point for receiving and one connecting point for transmitting. Reducing connecting points between a RF unit  220  and baseband chip  210  simplifies the design of baseband chip  210  and reduces its packaging costs.  
         [0026]    [0026]FIG. 2B shows one embodiment in which one connecting point at a line  2300  is used for both receiving and transmitting. In this FIG. 2B, a RF unit  220  is connected at line  2300  with baseband chip  210 . RF unit  220  includes a tristate buffer  240 R and a tristate buffer  240 T, and baseband chip  210  includes a tristate buffer  250 R and a tristate buffer  250 T. In the receiving mode, buffers  240 R and  250 R are enabled while buffers  240 T and  250 T are disabled so that the data on line  2400 R travels through buffer  240 R, line  2300 , and buffer  250 R, to line  2500 R. Similarly, in the transmitting mode, buffers  240 R and  250 R are disabled while buffers  240 T and  250 T are enabled so that the data on line  2500 T travels through buffer  250 T, line  2300 , and buffer  240 T, to line  2500 T.  
       The RF Unit  
       [0027]    [0027]FIG. 3 shows a unit  220  including L number of sub units  2200 , e.g., sub unit  2200 ( 1 ) to sub unit  2200 (L), in accordance with one embodiment. As discussed above, each sub unit  2200  is connected to at least one antenna, and the number of antennas per sub unit  2200  can be conveniently selected. In one embodiment, the distance between two antennas equals to ¼ of the wavelength of the carrier or wallet frequency of the antenna. A wavelength of a signal is one over the frequency of that signal. For illustrative purposes, FIG. 3 shows that each RF sub unit  2200 ( 1 ) to  2200 (L) is connected to an antenna  310 ( 1 ) to  310 (L), respectively. Each antenna  310  is associated with a carrier RF frequency F( 1 ) to F(L). Each sub unit  2200 , down-converts each RF frequency F( 1 ) to F(L) into each intermediate frequency (IF), which, through a serializing process, is transformed into each frequency F″( 1 ) to F″(L), respectively. For illustration purposes, the data received from each antenna  310  is referred to as data D( 1 ) to data D(L), respectively. Each sub unit  2200  also transforms data D( 1 ) to data D(L) into data D″( 1 ) to data D″(L), respectively, each of which corresponds to each frequency F″.  
         [0028]    In FIG. 3, RF sub units  2200  are connected serially or as a daisy chain. That is, a first sub unit is connected to a second sub unit, the second sub unit is connected to a third sub unit, etc., and the last sub unit is connected to baseband chip  210 . FIG. 3 shows that sub unit  2200 (L) is connected to sub unit  2200 (L−1) at line  3100 (L); sub unit  2200 (L−1) is connected to sub unit  2200 (L−2) at line  3100 (L−1); sub unit  2200 (L−2) is connected to sub unit  2200 (L−3) at line  3100 (L−2), etc., until sub unit  2200 ( 2 ) is connected to sub unit  2200 ( 1 ) at line  3100 ( 2 ). Further, sub unit  2200 ( 1 ) (or RF unit  220  as a whole) is connected to baseband chip  210  at line  3100 ( 1 ), which is a line  2300  in FIG. 2A. For illustration purposes, the data transmitted at line  3100 ( 1 ) to line  3100 (L) are referred to as data D′( 1 ) to D′(L). Similarly, the frequency transmitted at line  3100 ( 1 ) to line  3100 (L) is referred to as frequency F′( 1 ) to frequency F′(L), respectively.  
         [0029]    In one embodiment of a receiving mode, data D′(L) on line  3100 (L) corresponds to data D″(L). Data D′(L) is sent through sub unit  2200 (L−1), which combines data D″(L−1) and data D′(L) to form data D′(L−1) on line  3100 (L−1). Data D′(L−1) is sent through sub unit  2200 (L−2), which combines data D″(L−2) and data D′(L−1) to form data D′(L−2), etc. Finally, data D′( 2 ) is sent through sub unit  2200 ( 1 ), which combines data D″( 1 ) and data D′( 2 ) to form data D′( 1 ) online  3100 ( 1 ). In fact, data D′( 1 ) is the combined data of data D″( 1 ) to data D″(L). Further, if I is an integer, then data D′(I) is the combined data of data D′(I) and data D′(I+1). For example, if L equals to 4 and I equals to 2 then data D′( 2 ) is the combined data of data D″( 2 ) and data D′( 3 ), wherein data D′( 3 ) is the combined data of data D″( 3 ) and data D″( 4 ).  
         [0030]    In one embodiment of a transmitting mode, data D′( 1 ) on line  3100 ( 1 ) corresponds to the combined data D″( 1 ) to D″(L). Data D′( 1 ) is sent to sub unit  2200 ( 1 ), which keeps the data D″( 1 ) for itself and sends the rest of the data to sub unit  2200 ( 2 ) on line  3100 ( 2 ). Sub unit  2200 ( 2 ) keeps the data D″( 2 ) for itself and sends the rest of the data to sub unit  2200 ( 3 ) on line  3100 ( 3 ), etc. Finally, data D′(L), which corresponds to data D″(L), is sent through line  3100 (L) to sub unit  2200 (L). In the above discussion, each sub unit  2200 ( 1 ) to  2200 (L), through a up-converting process, transforms data D″( 1 ) to D″(L) into data D( 1 ) to D(L), which is sent through antenna  310 ( 1 ) to antenna  310 (L), respectively.  
         [0031]    Each RF frequency F can be any frequency within the electromagnetic spectrum associated with radio wave propagation, and can be different for one antenna  310  to another antenna  310 . However, in various embodiments, all frequencies F are substantially the same, and are compatible with the IEEE 802.11 standard, which runs at 2.4 GZ to 5.0 GHZ. Further, frequency F′( 1 ) to F′(L) corresponds to the frequency of data D′( 1 ) to data D′(L), respectively. Additionally, frequency F″(L) corresponds to frequency F″(L); frequency F′(L−1) is the sum of frequency F″(L−1) and frequency F′(L); frequency F′(L−2) is the sum of frequency F″(L−2) and frequency F′(L−1); and frequency F′( 1 ) is the sum of frequency F″( 1 ) and frequency F′( 2 ) or the sum of all frequency F″( 1 ) to frequency F″(L). If I is an integer, then frequency F′(I) is the sum of frequency F″(I) and frequency F′(I+1). For illustrated purposes, let L equals to 4 and each frequency F″( 1 ) to F″( 4 ) equals to 10 MHZ, then frequency F′( 1 ) equals to 40 MHZ (10 MHZ*4).  
         [0032]    In one embodiment, the maximum frequency allowable for frequency F′( 1 ), or the maximum frequency allowable at line  3100 ( 1 ), determines the maximum number of RF sub units  2200  allowable in a daisy chain in a unit  220 . This maximum frequency allowable for frequency F′( 1 ) varies depending on various factors, including, for example, the material forming the printed-circuit board (PCB) implementing RF units  220  and baseband chip  210 , the noise tolerance of the PCB, the distance between RF units  220  and baseband chip  210 , etc. In general, the longer the distance, the lower the frequency is allowable because of the noise coupling and signal distortion, etc. If each frequency F″ of each RF sub unit  2200  equals to each other, then the maximum number of sub units  2200  allowable in a daisy chain in a unit  220  is obtained by dividing the maximum frequency allowable for frequency F′( 1 ) by the frequency F″. Consequently, if each frequency F″ equals to 10 MHZ, and the maximum frequency allowable for frequency F′( 1 ) is 100 MHZ, then the maximum number of sub units  2200  allowable in the daisy chain is 10 (100 MHZ/10 MHZ). Similarly, if the maximum frequency allowable for F′( 1 ) is 150 MHZ, then the maximum number of sub units  2200  allowable in the daisy chain is 15 (150 MHZ/10 MHZ), etc.  
         [0033]    In one embodiment, each sub unit  2200  is removably connected to another sub unit in unit  220 . Consequently, depending on the number of antennas desired for a particular application, a combination of a number of antennas per sub unit  2200 , a number of sub units  2200  per unit  220 , and a number of units  220  per baseband chip  210  may be selected. For example, if six antennas are desired, then two antennas per each sub units  2200 , and three sub units  2200  per each unit  220  may be selected. Alternatively, one antenna per each sub unit  2200 , three sub units  2200  per unit  220 , and two units  220  may be selected, etc. The invention is not limited to a number of antennas per sub unit  2200 , a number of sub units  2200  per unit  220 , or a number of units  220  connected to baseband chip  210 . As additional antennas are added to a sub unit  2200 , additional sub units  2200  are added to units  220 , and/or additional units  220  are added to baseband chip  210 , additional antennas are added to baseband chip  210 . Alternatively speaking, additional antennas are added to smart antenna  120  and access point  125 .  
         [0034]    Because RF sub units  2200  are connected serially to each other and to baseband chip  210 , connecting L number of RF sub units  2200  in an RF unit  220  to baseband chip  210  requires one connecting point or interface. This connecting point is also the connecting point of a RF unit  220  to baseband chip  210  at a line  2300  in FIG. 2A or a line  3100 ( 1 ) in FIG. 3. If the L number of RF sub units  2200  were to be connected in parallel to baseband chip  210 , then L number of connecting points would be required because each number of RF sub unit  2200  requires one connecting point. Reducing the number of connecting points for baseband chip  210  reduces its packaging costs. Each RF sub unit  2200  may be removably connected to each other by any convenient mechanism. In embodiments where printed circuit boards (PCBs) are used to implement sub units  2200 , any mechanism for connecting PCBs is effective.  
       The Data in the Receiving Mode  
       [0035]    Referring to FIG. 4 for an illustration of how data D″( 1 ) to D″(L) is combined into data D′( 1 ) on line  3100 ( 1 ), in accordance with one embodiment. For illustration purposes, there are four sub units  2200  in a unit  220 , i.e., L equals to 4. Further, each stream of data D″( 1 ) to data D″( 4 ) runs at a 10 MHZ frequency. On line  1 , sub unit  2200 ( 4 ) transmits data D″( 4 ) to line  3100 ( 4 ) as data D′( 4 ) running at 10 MHZ frequency. On line  2 , sub unit  2200 ( 3 ) combines data D″( 3 ) and data D′( 4 ) to form data D′( 3 ) running at 20 MHZ. Data D′( 3 ) includes data D″( 3 ) and D″( 4 ). On line  3 , sub unit  2200 ( 2 ) combines data D″( 2 ) and data D′( 3 ) to form data D′( 2 ) running at 30 MHZ. Data D′( 2 ) includes data D″( 2 ), D″( 3 ), and D″( 4 ). On line  4 , sub unit  2200 ( 1 ) combines data D″( 1 ) and data D′( 2 ) to form data D′( 1 ) running at 40 MHZ. Data D′( 1 ) includes data D″( 1 ), D″( 2 ), D″( 3 ), and D″( 4 ). FIG. 4 shows data D′( 3 ), D′( 2 ), and D′( 1 ) having data D″ in the order of D″( 4 ) and D″( 3 ); D″( 4 ), D″( 3 ), and D″( 2 ); and D″( 4 ), D″( 3 ), D″( 2 ), and D″( 1 ), respectively. However, the invention is not limited to a particular order of data D″ in each data D′. Any order of data D″ in each data D′ is within the scope of the invention. For example, data D′( 3 ), D′( 2 ), and D′( 1 ) may include data D″ in the reverse order shown in FIG. 4. That is, data D′( 3 ), D′( 2 ), and D′( 1 ) may include data D″ in the order of D″( 3 ) and D″( 4 ); D″( 2 ), D″( 3 ), and D″( 4 ), and D″( 1 ), D″( 2 ), D″( 3 ), and D″( 4 ), respectively, etc. In embodiments where the order of data D″ in data D′( 1 ) is not predictable, each data D″ is earmarked so that baseband chip  210  can identify data D″ in data D′( 1 ).  
       The Data in the Transmitting Mode  
       [0036]    Referring to the same FIG. 4 for an illustration of how data is transmitted from baseband chip  210  to each RF sub unit  2200  in a unit  220 . On line  4 , baseband chip  210  sends data D″( 4 ), D″( 3 ), D″( 2 ), and D″( 1 ) as data D′( 1 ) on line  3100 ( 1 ) to sub unit  2200 ( 1 ). Data D′( 1 ) runs at a 40 MHZ frequency. Sub unit  2200 ( 1 ) keeps data D″( 1 ) for itself, and, as shown on line  3 , sends data D″( 4 ), D″( 3 ), and D″( 2 ) as data D′( 2 ) to sub unit  2200 ( 2 ). Data D′( 2 ) runs at 30 MHZ. Sub unit  2200 ( 2 ) keeps data D″( 2 ) for itself, and, on line  2 , sends data D″( 4 ) and D″( 3 ) as data D′( 3 ) to sub unit  2200 ( 3 ). Data D′( 3 ) runs at 20 MHZ. Sub unit  2200 ( 3 ) keeps data D″( 3 ) for itself, and, on line  1 , sends data D″( 4 ) as data D′( 4 ) to sub unit  2200 ( 4 ). Data D′( 4 ) runs at 10 MHZ.  
       The RF Sub Unit  
       [0037]    [0037]FIG. 5 shows a RF sub unit  2200  having a receiving unit  504  and a transmitting unit  508 , in accordance with one embodiment. Receiving unit  504  receives data from antenna  310  through line  5100 , processed the data, and sends the processed data through line  5300  and line  3100  to baseband chip  210 . Baseband chip  210  sends the data through line  3100  and line  5400  to transmitting unit  508 , which processes the data, and sends the processed data through line  5200  to antenna  310 . Depending on applications, lines  5300  and  5400  may be implemented as lines  2400 R and  2500 T in FIG. 2B, respectively.  
       The Receiving Unit  
       [0038]    [0038]FIG. 6 shows a receiving unit  504  in accordance with one embodiment. Receiving unit  504  includes a down-converter  605 , an analog-to-digital converter (ADC)  610 , a serializer  620 , and an interleaver  630 . Down-converter  605  converts the radio frequency of the signals on line  6050  to the intermediate frequency on line  6100 . The signal on line  6050  is the data received from antenna  310  and corresponds to data D running at a frequency F in FIG. 3. Line  6050  also corresponds to line  5100  in FIG. 5. ADC  610  converts the data in analog form on line  6100  to digital form on line  6150 . Serializer  620  converts the data on line  6150  to the data on line  6250 , which, in one embodiment, corresponds to data D″ in FIG. 3. Interleaver  630  combines data D″ on line  6250  and the data on line  6270  to form the data on line  6300 , which corresponds to line  5300  in FIG. 5. If I is an integer, and if receiving unit  604  is in a sub unit  2200 (I) in FIG. 3, then line  6300  corresponds to line  3100  (I) while line  6270  corresponds to line  3100  (I+1). For example, if I equals to 1 then line  6300  corresponds to line  3100 ( 1 ) while line  6270  corresponds to line  3100 ( 2 ). If I equals to 3 then line  6300  corresponds to line  3100 ( 3 ) while line  6270  corresponds to line  3100 ( 4 ), etc. If I equals to L, then line  6300  corresponds to line  3100 (L), and there is no line  6270 .  
       The Interleaver  
       [0039]    [0039]FIGS. 7A and 7B show two different types of interleaver  630 , in accordance with one embodiment. In FIG. 7A, interleaver  630 (L) corresponds to a RF sub unit  2200 (L), which is the last sub unit in a daisy chain. Interleaver  630 (L) includes a buffer  710 A that passes data D″(L) on line  6250  as data D′(L) on line  3100 (L). If L equals to 4, then data D″( 4 ) equals to D′( 4 ) shown on line  1  in FIG. 4.  
         [0040]    [0040]FIG. 7B shows an interleaver  530 (I) corresponding to a RF sub unit  2200 (I). Interleaver  530 (I) includes a multiplexer (mux)  710 B having lines  6250 (I) and  3100 (I+1) as inputs and line  3100 (I) as output. The data on line  6250 (I) and on line  3100 ( 1 +1) corresponds to data D″(I) running at a 10 MHZ frequency and D′(I+1) running at a frequency of 10 MHZ*(L−I). For each 100 NS period of the output, mux  710 B selects the data on line  6250 (I) in the first 100 NS/(L−I+1), and selects the data on line  3100 ( 1 +1) in the next (L−I) times, each for a period of 100 NS/(L−I+1), resulting in data D′(I) on line  3100 (I) running at 100 NS/(L−I+1) periods or a (L−I+1)*10 MHZ frequency.  
         [0041]    For example, if L equals to 4, and I equals to 3, then line  6250 (I) corresponds to line  6250 ( 3 ) and line  3100 ( 1 +1) equals to line  3100 ( 4 ). The data on line  6250 ( 3 ) and on line  3100 ( 4 ) correspond to data D″( 3 ) and D′( 4 ), which corresponds to data D″( 4 ), respectively, each of which runs at a 10 MHZ frequency or a plurality of 100 NS periods. For each 100 NS period of the output, mux  710 B selects data D″( 3 ) on line  6250 ( 3 ) for the first 50 NS, and selects data D′( 4 ) on line  3100 ( 4 ) for the second 50 NS, resulting in data D′( 3 ) on line  3100 ( 3 ) running at 50 NS periods or a 20 MHZ frequency. Data D′( 3 ) is shown on line  2  in FIG. 4.  
         [0042]    If L equals to 4, and I equals to 2, then line  6250 (I) corresponds to line  6250 ( 2 ) and line  3100 (I+1) corresponds to line  3100 ( 3 ). The data on line  6250 ( 2 ) and on line  3100 ( 3 ) correspond to data D″( 2 ) running at a 10 MHZ frequency and data D′( 3 ) running at a 20 MHZ frequency. For each 100 NS period of the output, mux  710 B selects data D″( 2 ) on line  6250 ( 2 ) in the first 33.33 NS, and selects the data on line  3100 ( 3 ) in the next two 33.33 NS, resulting in data D′( 2 ) on line  3100 ( 2 ) running at 33.33 NS periods or a 30 MHZ frequency. Data D′( 2 ) is shown on line  3  in FIG. 4.  
         [0043]    If L equals to 4, and I equals to 1, then line  6250 (I) corresponds to line  6250 ( 1 ), and line  3100 (I+1) corresponds to line  3100 ( 2 ). The data on line  6250 ( 1 ) and on line  3100 ( 2 ) correspond to data D″( 1 ) running at a 10 MHZ frequency and data D′( 2 ) running at a 30 MHZ frequency. Data D′( 2 ) is the combination of data D″( 4 ) and data D″( 3 ). For each 100 NS period of the output, mux  710 B selects data D″( 1 ) on line  6250 ( 1 ) in the first 25 NS, and selects data D′( 2 ) on line  3100 ( 2 ) in the next three 25 NS, resulting in data D′( 1 ) on line  3100 ( 1 ) running at 25 NS periods or a 40 MHZ frequency. Data D′( 1 ) is shown on line  4  in FIG. 4.  
       The Transimitting Unit  
       [0044]    [0044]FIG. 8 shows a transmitting unit  508  of FIG. 5, in accordance with one embodiment. Transmitting unit  508  includes a de-interleaver  810 , a de-serializer  820 , a digital to analog (DAC)  830 , and an up-converter  840 .  
         [0045]    De-interleaver  810  separates the data on line  8050  into the data on line  8100  and the data on line  8150 . Line  8050  corresponds to line  5400  in FIG. 5. If I is an integer, and if receiving unit  508  is in a sub unit  2200 (I) in FIG. 3, then line  8050  corresponds to line  3100  (I) while line  8150  corresponds to line  3100  (I+1). For example, if I equals to 1 then line  8050  corresponds to line  3100 ( 1 ) while line  8150  corresponds to line  3100 ( 2 ). If I equals to 3 then line  8050  corresponds to line  3100 ( 3 ) while line  8150  corresponds to line  3100 ( 4 ), etc. If I equals to L, then line  8050  corresponds to line  3100 (L), and there is no line  8150 .  
         [0046]    De-serializer  820  converts the data on line  8100  to the data on line  8200 . The data on line  8100 , in one embodiment, corresponds to data D″ in FIG. 3. DAC  830  converts the data in digital form on line  8200  to analog form on line  8300 . Up-converter  840  converts the intermediate frequency of the data on line  8300  to the radio frequency on line  8400 . The data on line  8400  corresponds to data D running at a frequency F in FIG. 3 and is transmitted to antenna  310 . Line  8400  also corresponds to line  5200  in FIG. 5  
       The De-Interleaver  
       [0047]    [0047]FIGS. 9A and 9B show two different types of de-interleavers  810 , in accordance with one embodiment. FIG. 9A shows a de-interleaver  810 ( 1 ) corresponding to a RF sub unit  2200 (I). De-interleaver  810 (I) includes a de-mux  910 A having line  3100 (I) as input and lines  8100 (I) and  3100 (I+1) as outputs. The data on line  3100 (I) runs at a (L−I+1)* 10 MHZ frequency and includes the data D″(I) to data D″(L). For each 100 NS of data D′(I), de-mux  910 A assigns the first 100 NS/(L−I+1) to line  8100 ( 1 ) running at 10 MHZ and the next (L−I) times of 100 NS/(L−I+1) to line  3100 ( 1 +1) running at (L−I)*10 MHZ. The data on line  8100 (I) corresponds to data D″(I) while the data on line  3100 (I+1) corresponds to data D′(I+1).  
         [0048]    If L equals to 4, and I equals to 1, then line  3100 (I) corresponds to line  3100 ( 1 ), line  8100 (I) corresponds to line  8100 ( 1 ), and line  3100 ( 1 +1) corresponds to line  3100 ( 2 ). The data on line  3100 ( 1 ) corresponds to data D′( 1 ) and runs at a 40 MHZ frequency or 25 NS periods. Data D′( 1 ) includes the data D″( 1 ), data D″( 2 ), data D″( 3 ), and data D″( 4 ). For each 100 NS of data D′( 1 ), de-mux  910 A assigns the first 25 NS to line  8100 ( 1 ) running at 10 MHZ and the next three 25 NS to line  3100 ( 2 ) running at 30 MHZ. The data on line  8100 ( 1 ) corresponds to data D″( 1 ) while the data on line  3100 ( 2 ) corresponds to data D′( 2 ). Data D′( 1 ) is shown on line  4  and data D′( 2 ) is shown on line  3  in FIG. 4.  
         [0049]    If L equals to 4, and I equals to 2, then line  3100 (I) corresponds to line  3100 ( 2 ), line  8100 (I) corresponds to line  8100 ( 2 ), and line  3100 (I+1) corresponds to line  3100 ( 3 ). The data on line  3100 ( 2 ) corresponds to data D′( 2 ) and runs at a 30 MHZ frequency or 33.33 NS periods. Data D′( 2 ) includes data D″( 2 ), data D″( 3 ), and data D″( 4 ). For each 100 NS of data D′( 2 ), de-mux  910 A assigns the first 33.33 NS to line  8100 ( 2 ) running at 10 MHZ and the next two 33.33 NS to line  3100 ( 3 ) running at 20 MHZ. The data on line  8100 ( 2 ) corresponds to data D″( 2 ) while the data on line  3100 ( 3 ) corresponds to data D′( 3 ). Data D′( 2 ) is shown on line  3  and data D′( 3 ) is shown on line  2  in FIG. 4.  
         [0050]    If L equals to 4, and I equals to 3, then line  3100 (I) corresponds to line  3100 ( 3 ), line  8100 (I) corresponds to line  8100 ( 3 ), and line  3100 (I+1) corresponds to line  3100 ( 4 ). The data on line  3100 ( 3 ) corresponds to data D′( 3 ) and runs at a 20 MHZ frequency or 50 NS periods. Data D′( 3 ) includes data D″( 3 ) and data D″( 4 ). For each 100 NS of data D′( 3 ), de-mux  910 A assigns the first 50 NS to line  8100 ( 3 ) running at 10 MHZ and the next 50 NS to line  3100 ( 4 ) running at 10 MHZ. The data on line  8100 ( 3 ) corresponds to data D″( 3 ) while the data on line  3100 ( 4 ) corresponds to data D′( 4 ), which corresponds to data D″( 4 ). Data D′( 3 ) is shown on line  2  and data D′( 4 ) is shown on line  1  in FIG. 4.  
         [0051]    In FIG. 9B, de-interleaver  810 (L) corresponds to a RF sub unit  2200 (L), which is the last sub unit in a daisy chain. De-interleaver  810 (L) includes a buffer  910 B that passes data D′(L) on line  3100 (L) as data D″(L) on line  8100 (L). If L equals to 4, then data D″( 4 ) equals to data D′( 4 ) shown on line  1  in FIG. 4.  
       The Baseband Chip  
       [0052]    [0052]FIG. 10 shows a baseband chip  210  in accordance with one embodiment. Chip  210  includes an interface  1010  and a smart-antenna DSP engine  1020 .  
         [0053]    Interface  1010  receives data D″( 1 ) to data D″(L) in the combined form for each line  2300 ( 1 ) to  2300 (M) in FIG. 2A. The data on line  2300  for each RF unit  220  corresponds to data D′( 1 ) on line  3100 ( 1 ) in FIG. 3. In the receiving mode, for each RF unit  220 , interface  1010  separates the combined data D′( 1 ) to each data D″ corresponding to each RF sub unit  2200  and its associated antenna  310 . In one embodiment, interface  1010  recognizes data D″ of each RF sub unit based on the order the data D″ is sent to interface  1010 . For example, in the example of FIG. 4, for each RF unit  220 , interface  1010  receives data D′( 1 ) in the order of sub unit  2200 ( 1 ) to sub unit  2200 (L), e.g., in the order of data D″( 1 ) to data D″(L). Recognizing the frequency and the order of data D″ in data D′( 1 ), interface  1010  can identify D″ for each sub unit  2200 . In the above example that L equals to 4, data D′( 1 ) received at interface  1010  runs at a 40 MHZ frequency or a plurality of 25 NS periods. In the same example, for each 100 NS data D′( 1 ) includes the data in the order of data D″( 1 ), data D″( 2 ), data D″( 3 ), and data D″( 4 ) for the first, the second, the third, and the fourth 25 NS, respectively. Consequently, interface  1010  can accordingly identify each data D″. Alternatively, interface  1010  can use a signal earmarked in data D″ and thus data D′( 1 ) to identify data D″. Data D″ is earmarked when it is sent through its corresponding RF sub units  2200 . The invention is not limited to a method for interface  1010  to recognize the data and its associated antenna.  
         [0054]    Conversely, in the transmitting mode, when interface  1010  sends data to a RF unit  220 , interface  1010  combines the data corresponding to each RF sub units  2200  into data D′( 1 ) which runs at a frequency being the sum of the frequency of the data D″ for each sub unit  2200 . Each sub unit  2200 , via its de-interleaver, keeps the data for itself, and sends the rest of the data to the next sub unit  2200  as explained above.  
         [0055]    Smart antenna DSP engine  1020  uses the adaptive array techniques to process the data accordingly. For example, in the receiving mode, engine  1020  processes the data received from each antenna  310 , e.g., data D″( 1 ) to data D″(L), then sends the processed data to be further processed by the network layers such as the physical layer (PHY) and the media access control (MAC) layer. The data is eventually sent to the network, which in one embodiment is the LAN. Similarly, in the transmitting mode, engine  1020  receives the data from the LAN via the network layers, processes the data, then sends the data to interface  1010 , etc.  
         [0056]    In the foregoing, the invention has been described with reference to various embodiments. However, those skilled in the art will recognize that the invention is not limited to those embodiments; variations and modifications may be made without departing from the scope of the invention; and the specification including the drawings is to be regarded as illustrative rather than as restrictive.