Abstract:
Individual RF cables span between element/transceiver pairs in traditional beam forming systems, and the number of elements in an array used for beam forming is thus restricted. To reduce the number of RF cables but maintain or increase the number of elements in an antenna array, an embodiment of the present invention includes electronics at the base of an antenna tower that apply digital multiplexing codes to signals communicated to electronics located at the top of the antenna tower. The electronics at the top demultiplex the signals and transmit them via the antenna array. Received RF signals are processed in a like manner in a reverse direction. Fewer transmission paths (e.g., RF or fiber optic cables) than the number of elements in the antenna array can be used. More antenna elements provide benefits, such as higher user capacity, more antenna beams, narrower antenna beams, and higher in-building penetration.

Description:
RELATED APPLICATION(S)  
       [0001]     This application is a divisional of U.S. application Ser. No. 09/791,503, filed on Feb. 23, 2001, which claims the benefit of U.S. Provisional Application No. 60/184,754, filed on Feb. 24, 2000, the entire teachings of the above application(s) are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     In wireless voice and data communications, it is desirable to maximize the number of users in a base transceiver station (BTS) sector while at the same time providing high signal quality (i.e., high SNR) for the users. One way to achieve both conditions is through the use of a beam forming antenna. A BTS can generate plural directed beams by employing an antenna array and digitizing signals transmitted to and received from the antenna array in a weighted manner (i.e., amplitude and/or phase) that produces the plural beams. Since the beams have high gain in the direction of the main lobe of the composite beam, high SNR is achieved. And, since the BTS can change the weights associated with each antenna element in the array to cause the beam to scan, a high gain can be maintained throughout the duration of a user&#39;s wireless connection with the base station.  
         [0003]      FIG. 1  is a schematic diagram of a wireless communications network  100  having three base transceiver stations  105   a,    105   b,    105   c.    
         [0004]     The first BTS  105   a  provides three beams  107   a,    107   b,  and  107   c  produced by beam forming. The first beam  107   a  is used for communicating to a first user  109   a  in the first BTS sector. The first user  109   a  is inside a building  108 . Because the first beam  107   a  is produced through the use of beam forming, it has excess link margin to allow deeper penetration into the building  108  for communicating with the user  109   a.  Further, multi-path noise caused by a beam reflecting off other buildings is minimized or avoided due to the formed beam  107   a.    
         [0005]     The first BTS  105   a  produces a second beam  107   b  to communicate with a second user  109   b  in the first BTS sector. In this case, the second beam  107   b  is purposely kept short so as to reduce pilot pollution where BTS sectors intersect.  
         [0006]     The first BTS  105   a  also produces a third beam  107   c  for communicating with a third user  109   c  in the first BTS sector. Similar to the first beam  107   a,  the third beam  107   c  reduces multipath noise effects due to its directiveness. Also, the third user  109   c  is closer to the third BTS  105   c;  but, because of the high gain produced by beam forming, the third beam  107   c  of the first BTS  105   a  is able to reach the third user  109   c  to assist the third BTS  105   c,  which is heavily loaded with other users, as will be discussed. The antenna gain is proportional to 20 LOG(number of elements) plus vertical gain. For example, for a sixteen element array four feet wide, the beam forming may provide over thirty-seven dB versus fifteen dB for conventional antennas.  
         [0007]     The second BTS  105   b  provides two beams,  111   a,    111   b  produced by beam forming. The first beam  111   a  communicates with a first user  113   a  in the second BTS sector. The second beam  111   b  provides a link to a second user  113   b  in the second BTS sector. Because of the high-link margin produced by beam forming, sparse initial deployment provides lower initial capital requirements for the wireless communications network  100 .  
         [0008]     The third BTS  105   c  is able to provide four beams  115   a,    115   b,    115   c,    115   d  in a beam forming manner to communicate with high-gain to four users  117   a,    117   b,    117   c,  and  117   d,  respectively.  
         [0009]     As can be seen from the beams  107 ,  111 ,  115  produced by the base transceiver stations  105 , the use of beam forming eliminates noise problems caused by multipath, pilot signal pollution, and interference from signals from adjacent base transceiver stations. Further, the high gains afforded by the beams produced by the beam forming provides a so-called virtual point-to-point RF effect.  
         [0010]      FIG. 2A  is a block diagram of the prior art base transceiver station  105   a.  The base transceiver station  105   a  has an antenna assembly  205 , base electronics  210 , and base station tower  215 . The base electronics  210  comprise transceivers  220 , weighting electronics (e.g., Butler Matrix, FFT or other)  225 , and user channel cards  230 .  
         [0011]     As shown in detail in  FIG. 2B , the transceivers  220  each comprise a transmitter  235 , receiver  240 , and duplexer  245 . The duplexer  245  is coupled to a single element  255  in a sector antenna array  250 , as shown in  FIG. 2C . The coupling between the transceivers  220  and the elements  255  of the sector antenna array  250  is made via parallel cables  265   a,    265   b,    265   c,  and so on. The number of parallel cables used is equal to the number of transceiver/element pairs. Each cable is expensive, heavy, and sensitive to temperature changes. Similarly, the transceivers are expensive, relatively large in size, and sensitive to temperature and humidity changes.  
         [0012]     Continuing to refer to  FIG. 2A , extending upward from the base electronics  210  is an antenna assembly support pole  260 , on which the sector antenna array(s)  250  is/are supported. Typically, antenna assembly support pole  260  is capable of supporting nine parallel cables  265 . Because (i) it is useful to have three sector antenna arrays  250  for transmitting and receiving in 360° and (ii) each sector antenna array  250  preferably includes at least four elements  255 , nine parallel cables  265  is limiting to the capacity of the base transceiver station  105   a.    
       SUMMARY OF THE INVENTION  
       [0013]     The problem with traditional beam forming systems is that the number of RF transceiver systems required in a base terminal station (BTS) adds complexity and cost to the system. RF transceivers, including cabling and other associated components, have performance characteristics that must be calibrated to match each other in order to make the beam forming operate properly. Since the RF transceiver, cabling, and other associated components tend to have gain and phase offset drift over time, temperature, and humidity, the traditional beam forming system must be supported by plural, expensive, calibration electronics to maintain performance.  
         [0014]     Moreover, in traditional beam forming systems, the weight and size of RF cabling tends to be significant for single-pole structures that support the antenna arrays. Typical single-pole structures can handle nine RF cables. Since, in traditional beam forming systems, each element in an antenna array requires an individual RF cable spanning between the element/transceiver pairs, the number of elements in an array used for beam forming is restricted in number for single-pole structures.  
         [0015]     Cost/benefit analysis shows that a maximum of four antenna elements are practical in traditional beam forming systems. Fewer antenna elements in an antenna array result in fewer users that can be supported by a beam forming system at any one time. Also, fewer antenna elements produce a broader beam than a higher number of antenna elements. The broader beam tends to be a restriction on overall system performance because it is a lower antenna gain than a narrower beam (i.e., 3 dB gain for one-half the beam width), among other reasons.  
         [0016]     Addressing the problems of the prior art beam forming systems, the principles of the present invention apply digital multiplexing techniques to a beam forming system to reduce RF components and improve system performance. The reduction in RF components eliminates the need for RF channel-to-RF channel calibration and reduces weight, complexity, and cost. Reducing weight, complexity, and cost allows the number of elements in the antenna array to be increased. More antenna elements results in at least the following benefits: higher user capacity, higher SNR, more antenna beams, narrower antenna beams, higher in-building penetration, and lower cost components.  
         [0017]     Accordingly, one aspect of the present invention is a method and system for receiving signals in a beam forming manner in a radio communication system. A signal is detected at a given element of plural elements forming an antenna array. A code corresponding to the given element is applied to the system at the given element to distinguish the signal from among plural signals received by the plural elements.  
         [0018]     The coded signals from the plurality of elements are summed together to form a code division multiplexed signal. The system then produces a composite baseband signal corresponding to the code division multiplexed signal. In one embodiment, producing the composite baseband signal includes (i) controlling the gain, (ii) down-converting the code division multiplexed signal, and (iii) sampling the code division multiplexed signal, or a representation thereof.  
         [0019]     The system may further extract the given signal from the given element. Extracting the given signal includes multiplying the composite baseband signal by the code applied to the given signal. The system then applies a weight to the extracted signal. Further, the system may (i) extract a subset of signals from the baseband signals, (ii) apply weights to the extracted signals, and (iii) sum the multiple weighted extracted signals to yield signals producing a spatial beam forming effect. This provides beam forming in a simple way.  
         [0020]     To produce beam forming in an elegant way, the system (a) replicates the codes applied to the signals at the elements, (b) applies weights to the replicated codes, (c) sums the coded weights to form a composite signal, (d) multiplies the received baseband composite signal by the weighted composite signal, (e) forms a single composite signal, and (f) integrates the single composite signal over the duration of the code to yield a spatial beam forming effect.  
         [0021]     Applying a code to the signal at the given element can be performed by modulating the code onto the RF signal. Then, the system samples a representation of the modulated RF signal, such as RF, baseband, or intermediate frequency (IF) representation, where the timing between the modulation and the sampling are locked to avoid sampling modulation-related transitions.  
         [0022]     The codes applied to the signal may be orthogonal codes. In one embodiment, the orthogonal codes are Walsh codes.  
         [0023]     The method and system just described may be deployed in a base station in the radio communication system.  
         [0024]     Another aspect of the present invention is a method and system for transmitting RF signals using beam forming in a radio communication system. The system receives a data signal to be transmitted from, say, a data network. The system then generates weights modulated by codes, which correspond to respective antenna elements. The coded weights are modulated with the data signal being transmitted to produce a coded, weighted signal for beam forming.  
         [0025]     The system may further modulate the coded weights with other data signals to be transmitted to produce respective, coded, weighted signals for beam forming. The coded, weighted signals can then be summed together to form a composite code division multiplexed signal. Further, the system converts the composite code division multiplexed signal to an analog representation, then up-converts the analog representation to an RF representation of the code division multiplexed signal.  
         [0026]     Still referring to transmitting RF signals, proximal to the antenna array, at a subset of elements in the antenna array, the system decomposes the composite RF representation into respective RF representations comprising at least one weight and at least one data signal to be transmitted corresponding to the respective elements to form at least one beam having a pattern formed by the respective weights. The weights include amplitude information, phase information, or a combination thereof to produce the formed beam.  
         [0027]     In transmitting, as in the case of receiving, the codes used by the system are typically orthogonal codes. In one embodiment, the orthogonal codes are Walsh codes.  
         [0028]     The methods and systems just described for receiving and transmitting RF signals using beam forming in a radio communication system may be deployed in a base station. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
         [0030]      FIG. 1  is a schematic diagram of a prior art wireless communication system employing beam forming;  
         [0031]      FIG. 2A  is a schematic diagram of a prior art base transceiver station employed in the wireless communication system of  FIG. 1 ;  
         [0032]      FIG. 2B  is a schematic diagram of a transceiver used in the base transceiver station of  FIG. 2A ;  
         [0033]      FIG. 2C  is a schematic diagram of a sector antenna array of  FIG. 2A ;  
         [0034]      FIG. 3A  is a schematic diagram of a split electronics approach embodiment of a base transceiver station producing beam forming according to the principles of the present invention deployable in the wireless communication system of  FIG. 1 ;  
         [0035]      FIG. 3B  is a schematic diagram of a transceiver used in the base transceiver station of  FIG. 3A ;  
         [0036]      FIG. 3C  is a schematic diagram of array electronics used in the base transceiver station of  FIG. 3A ;  
         [0037]      FIG. 3D  is a schematic diagram of weight multiplexer electronics used in the array electronics of  FIG. 3C ;  
         [0038]      FIG. 4A  is a block diagram of a symbol operated on by the base transceiver station system of  FIG. 3A ;  
         [0039]      FIG. 4B  is a block diagram of a chip composing a part of the symbol of  FIG. 4A ;  
         [0040]      FIG. 5A  is a schematic diagram of an integrated electronics approach embodiment of the base transceiver station of  FIG. 3A ;  
         [0041]      FIG. 5B  is a schematic diagram of array electronics used in the base transceiver station of  FIG. 5A ;  
         [0042]      FIG. 5C  is a schematic diagram of beam multiplexer electronics used in the array electronics of  FIG. 5B ;  
         [0043]      FIG. 6A  is a flow diagram of an embodiment of a receiving process in the base transceiver stations of  FIGS. 3A and 5A ;  
         [0044]      FIG. 6B  is a block diagram of a receiver module used in the receiving process of  FIG. 6A ;  
         [0045]      FIG. 7  is an abstract diagram of coding mathematics used in the receiving process of  FIG. 6A ;  
         [0046]      FIG. 8A  is a flow diagram of an embodiment of a transmitting process in the base transceiver stations of  FIGS. 3A and 5A ; and  
         [0047]      FIG. 8B  is a schematic diagram of a transmitter module used in the transmitting process of  FIG. 8A   
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0048]     A description of preferred embodiments of the invention follows.  
         [0049]      FIG. 3A  is a block diagram of a base transceiver station  300  in which the principles of the present invention are employed. The base transceiver station  300  includes an antenna assembly  302 , base electronics  306 , and base station tower  313 , on which the antenna assembly  302  is supported.  
         [0050]     The antenna assembly  302 , in this embodiment, includes three sector antenna arrays  305 . The sector antenna arrays  305  include electronics, described later, and elements  255 .  
         [0051]     The base electronics  306  include a single transceiver  370  for all elements  205  of the sector antenna arrays  305 . Further, the base electronics  306  include channel cards  365  with integrated weighting electronics, obviating separate weighting electronics  225  ( FIG. 2A ).  
         [0052]     The base station tower  313  include only a single RF cable  265   a  in this embodiment. In other embodiments, the RF cable  265   a  is replaced with a fiber optic cable, wire cable, or optical or radio frequency wireless link.  
         [0053]     The present invention simplifies the base transceiver station  300  using beam forming by using codes, such as orthogonal codes (e.g., Walsh codes), to code division multiplex the RF signals comprising data or information signals, where each code corresponds to a respective element  255  in the sector antenna array  305 . Once coded, the RF signals can then be transmitted on a single path (e.g., RF cable  265   a ) or subset of paths being fewer in number than the number of elements  255  in the antenna array  305 . It should also be understood that the same technique could be applied to data signals represented in intermediate-frequencies (IF) or baseband frequencies.  
         [0054]     The use of code division multiplexing shifts the high cost, high-complexity hardware of the prior art to low-cost, low-complexity digital techniques. The digital techniques can be applied to both transmit and receive functions of the communication system. The present invention does not change the mathematics of beam forming, just how the mathematics of beam forming are applied.  
         [0055]     The number of transceivers in the beam forming system can be reduced to as few as one transceiver for all elements  255  in the antenna array  305 . For three-sector array panels or other arrangements, the present invention allows a single transceiver to be used to support all elements in all three sectors.  
         [0056]     Since the number of RF cables, spanning between the RF transceiver(s)  370  and the antenna elements  255 , is equal to the number of RF transceivers  370 , the size and weight of the RF cabling is minimized by reducing the number of RF transceivers  370 .  
         [0057]     In an alternative embodiment, the transceiver(s)  370  is/are integrated into array electronics  308  that are deployed on the base station tower  313  with the elements  255  in the antenna array  305 . A fiber optic cable, for instance, carries data to/from the transceiver deployed on the tower and the base electronics  306  at the base of the tower. In this case, both the base electronics  306  and transceiver  370  are equipped with fiber optic communication means well known in the art.  
         [0058]     For receiving information signals (e.g. voice or data) having data to be transmitted, the code division multiplexing involves applying codes to the RF signal at the antenna elements  255  and summing the RF signals to form a composite (i.e., single) code division multiplexed signal. In individual baseband receiver modules, a weighted code generator generates code division multiplexed signals in which weights are coded with the same codes applied to the respective signals of the respective antenna elements. When the coded signals are modulated together, the signals and beam forming weights are extracted and multiplied as a result of the common codes, in a typical code division multiplexing manner.  
         [0059]     The code generators can be time-locked to ensure signal integrity. Further, A/D sampling of the RF signal can be synchronized to ensure sampling does not occur during modulation transitions, resulting in a high-quality modulator. In this way, perfect demodulation can be achieved with inexpensive electronic components.  
         [0060]     For transmitting the information signals, the receiving process is basically reversed. It should be noted that in conventional, non-beam forming systems, a single, transmitter power amplifier is used to increase the power of the transmitting RF signal. However, in the beam forming design, smaller, less-powerful transmitter power amplifiers are capable of being used, saving an order of magnitude in cost over a traditional transmitter amplifier.  
         [0061]     Referring to  FIG. 3B , the single transceiver  370  includes a transmitter  375  and a receiver  380 . The transmitter  375  transmits a composite Tx modulation signal, with beam weights for all elements  255 , from channel cards  365  to the array electronics  308 . Similarly, the receiver  380  receives a composite Rx signal from the array electronics  308  being sent to the channel cards  365 .  
         [0062]     The array electronics  308  are located proximal to the sector antenna array  305 . As shown in  FIG. 3C , inside the array electronics  308  is a splitter  310 , which receives RF signals via the RF Tx cable (not shown) in the RF cable  265   a  from the transmitter  375 . The splitter  310  splits the received signal to among plural weight multiplexer electronics (Mux Elx)  315 . The weight multiplexer electronics  315  are each coupled to respective elements  255  in respective sector antenna arrays  305 .  
         [0063]     The weight multiplexer electronics  315  also receive signals from a code generator, in this case a Walsh code generator  320 . The Walsh code generator  320  receives digital and timing control from the base electronics  306 . In the receiving path, the weight multiplexer electronics  315  provide RF signals to a summer  325 . The summer  325  transmits a composite RF Rx signal to the receiver  380  via an RF Rx cable (not shown) in the RF cable  265   a.    
         [0064]     As shown in  FIG. 3D , inside the weight multiplexer electronics  315 , there are circuits for transmitting an RF signal and receiving an RF signal. In the transmitting path, the RF signal is received from the splitter  310  by a modulator  330 . The RF signal is modulated with a Walsh code from the Walsh code generator  320  to extract the correct signal(s) and beam weighting(s) (i.e., intended for the associated antenna element) from the composite RF Tx modulation signal, as described in more detail in reference to  FIGS. 6A and 7 . The extracted signal is then filtered by a filter  335 , such as a bandpass filter, and amplified by a power amplifier  340 . The amplified signal is output from the transmitter power amplifier  340  to the respective antenna element  255  via a duplexer  345 , which alternates between transmit and receive in a typical manner.  
         [0065]     Continuing to refer to the weight multiplexer electronics  315 , in the receiving path, the antenna element  255  receives an RF Code Division Multiple Access (CDMA) signal from a mobile station (not shown). The received signal travels from the element  255  to the duplexer  345 . In turn, the duplexer  345  passes the received signal to a first filter  350 , such as a bandpass filter. Following the filter  350 , a low noise amplifier (LNA)  355  amplifies the received signal. The amplified received signal is then modulated by a modulator  330  with a Walsh code from the Walsh generator  320 . The coded RF signal is then filtered by a second filter  360 , such as a bandpass filter, and summed with other coded, received, RF signals—from other weight multiplexer electronics  315 —by a summer  325  to form a composite, coded, RF signal. The summer  325  then transmits the composite Rx signal from all elements  255  to the receiver  380  in the transceiver  370 .  
         [0066]     It should be understood that forming the composite coded signal can be done in other ways, such as placing summing units between the low-noise amplifier  335  and modulator  330 , without departing from the principles of the present invention.  
         [0067]     In operation, the base electronics  306  and array electronics  308  are processing symbols. A symbol is graphically illustrated in  FIG. 4A .  
         [0068]      FIG. 4A  is a block diagram of a symbol  400  having eight chips  405   a,    405   b,  . . . ,  405   h  (collectively  405 ). The chips occur at a given chip rate. For example, the given chip rate may be 1.2288 MHZ.  
         [0069]     A chip  405   a  is one bit of a pseudo-noise (PN) sequence. Each chip, such as chip  405   a,  is sampled a given number of times, such as eight times. The length of each sample corresponds to a multiplexing code period. To achieve the beam forming, the samples are further divided into bits  415 . Each bit  415  corresponds to a portion of a code applied to (i.e., dedicated to) a respective antenna element  255 ; therefore, the length of the code is typically equal to the number of antenna elements. So, for example, for eight antenna elements and a sample rate of eight samples per chip, it is said that the code is 64×. For a signal code rate of 1.2288 MHZ, the multiplexing code, Cm, is 64×1.2288. The multiplexing code, Cm, is discussed elsewhere herein as Walsh codes, Wi, or more generically as orthogonal codes. The codes may also be non-orthogonal codes.  
         [0070]     Referring again to  FIG. 3D , using the example provided in  FIG. 4A , following the LNA  355 , the chip rate is seen as 1.2288 MHZ. After modulating the chip rate with the Walsh code, the code rate is said to be 64×. Similar processing takes place in the transmitting path.  
         [0071]      FIG. 5A  is an alternative embodiment of the base station  300  employing the principles of the present invention. In the base station  500  of  FIG. 5A , the base electronics  306  include channel cards  515  with integrated weighting electronics. In this embodiment, the channel cards  515  transmit signals to be transmitted by the elements  255  of sector antenna array(s)  505  to mobile station(s) via a single fiber  520  for all three sector antenna arrays  505 .  
         [0072]     In the sector antenna arrays  505 , as shown in detail in  FIGS. 5B and 5C , array electronics  508  include a fiber transceiver  510  to transceive (i.e., transmit and/or receive) signals to and from the channel cards  515  in the base electronics  306 . The fiber transceiver  510  (i) passes received signals, optionally with some processing having been performed on the received signals, from the base electronics  306  to the transmitter  375  and (ii) transmits signals received from the receiver  380  to the base electronics  306 .  
         [0073]     By using a single fiber  520  for passing data between the base electronics  306  and the array electronics  508 , the weight of cabling is reduced from using RF cables to using the single fiber  520  for all three sectors. It should be understood that additional fibers to carry signals may be employed without departing from the principles of the present invention.  
         [0074]     Fiber optic communications have an advantage over RF communications in at least two ways: first, fiber optic communication components tend to be less sensitive to environmental conditions, such as temperature and humidity, and second, fiber optic communications keep EMI noise to a minimum, which is more difficult to control in the RF cable  265   a  ( FIG. 3A ).  
         [0075]      FIG. 6A  is a block diagram annotated with receiving processing flow. In the first step  605 , the signal RxSignalN (i.e., received RF signal) from a mobile station (not shown) is received by the N&#39;th element of the antenna array. It should be understood that a similar RF signal is received by each of the elements  255  of the respective sector antenna array.  
         [0076]     Following the first step  605 , the received RF signal is modulated with a Walsh code, Walsh N, by the modulator  330 . Following the filter  360 , the second step  610  is completed, at which point the signal received by the N&#39;th element of the antenna array is equal to WN*RxSignalN.  
         [0077]     Following the Summer Wilkenson combiner  632 , a third step  615  is completed. This third step results in a composite-received signal, which is represented by the following equation: CompositeRx=Σi(Wi*RxSignalk,i) at RF frequencies, where i indexes the elements and k indexes the individual information signals.  
         [0078]     In the receiver and A/D conversion, a fourth step is completed in which the composite-received signal at RF is converted into a baseband digital representation. The baseband digital representation of the composite received signal is represented by the following equation: CompositeRx=Σi(Wi*RxSignalk,i) at complex baseband.  
         [0079]     Alternatively, the composite-received signal at RF is converted into an intermediate-frequency (IF) representation and processed thereafter accordingly.  
         [0080]     In the complex baseband embodiment, the complex, baseband, composite, received signal is then processed by individual receiver modules  640 .  
         [0081]     Referring now to  FIG. 6B , in the individual receiver modules, a fifth step  625  is performed in which a weighted Walsh generator produces a composite weight signal at complex baseband, where the composite weight signal is represented by the following equation: CompositeWeight=Σi(Wi*Weightk,i) at complex baseband.  
         [0082]     In the weighted Walsh code generator  645 , a modulator (not shown) modulates the Walsh codes with the weights. The Walsh code generator  645  (i) produces the same Walsh codes as the Walsh codes used to code the received RF signals and (ii) is synchronized with the Walsh code generator generating the Walsh codes with which the received RF signal(s) is/are modulated. The weights correspond with the elements of the respective sector antenna array receiving the signals from the mobile station to produce a pre-determined spatial beam forming effect (i.e., beam pattern) to reconstruct the signal in a beam forming manner.  
         [0083]     The composite weight signal of step five  625  and composite received signal at baseband of the fourth step  620  are (i) modulated together by a modulator  650  in the individual receiver modules  640  then (ii) low-pass filtered by a digital low-pass filter  655 , which produces the results of step six  630 .  
         [0084]     The results of step six include a beam formed received signal, which is represented by the following equation at complex baseband: BeamFormedRxSignal(k)=Σ(Σi Wi*Weightk,i*Σi WiRxSignalk,i), where the external summation is performed over the duration of the multiplexing code. The equation can be reduced to the following equation: BeamFormedRxSignali=Σi(RxSignali*Weightk,i) at complex baseband. In this last equation, all Walsh modulation is removed and cross products have multiplied to near zero by the modulator  650  (see the discussion below in reference to  FIG. 7 ) and any remaining noise has been filtered off by the digital low pass filter  655 . In other words, the final equation represents the beam formed received signal.  
         [0085]      FIG. 7  is a graphical representation of the mathematics embedded in the receiving and transmitting processes occurring through the use of employing the Walsh codes. Walsh codes are orthogonal codes and are represented by the grid  705 , where the variable i is used to index the rows and the variable m is used to index the columns. The rows of the grid  705  are represented by the Walsh coded weights WiWeightk,i. The columns of the grid  705  are representative of the Walsh coded signal WiRxSignali,m. Because of the orthogonal quality of the Walsh codes, multiplying Walsh codes that are not the same go toward zero. Therefore, off-diagonal code match-ups  710  are “zeroed out,” as represented by the X&#39;s at off-diagonal row and column intersections. Codes that match up along the diagonal  715  are equal to or approximate unity. Thus, the weights and received signals associated with the codes that line up along the diagonal  715  are both multiplied together and multiplied by unity, whereas weights and received signals that are associated with off-diagonal code match-ups  710  are multiplied together and by zero, thus illustrating the results of step six  630  ( FIG. 6A ).  
         [0086]      FIG. 8A  is a schematic diagram of the transmitting processing flow. Inside each of plural transmitter modules  835 , as shown in detail in  FIG. 8B , a standard modulator  840  modulates a data signal to be transmitted. The modulated data signal is modulated with a weighted Walsh code generated by a weighted Walsh code generator  845 . The results of the first step  805  is produced by the weighted Walsh code generator  845 , where the weighted Walsh codes are represented by the following equation: CompositeWeight(j)=Σi(Wi*Weightj,i) at complex baseband, where j indexes the unique information signals and beams and i indexes the antenna elements  255 .  
         [0087]     The composite weight signal and the modulated data signal are modulated together by a modulator  850  that produces the result of the second step  810 , which is the beam to be transmitted. The beam to be transmitted in the second step  810  is represented by the following equation: BeamTx(j)=Σi(Wi*Weightj,i*TxSignalj) at complex baseband.  
         [0088]     Referring again to  FIG. 8A , each transmitting module  835  provides a digital representation of the transmission beam signal at complex baseband to a digital summer  855 . The output from the digital summer  855  produces the result of the third step  815 , which is the composite transmission signal represented by the following equation: CompositeTx=ΣjBeamTxj at complex baseband. This is the composite transmission signal to be transmitted by the antenna array to the users of the mobile stations (not shown) communicating with the base station system.  
         [0089]     A transmitter and D/A converter  860  provides the results for the fourth step  820 , which is a composite transmission signal at RF for all elements  255 , users, and sectors. Thus, the fourth step  820  includes all information for all beams being produced by the beam forming system. A Summer Wilkenson splitter  865  splits the composite transmission signal at RF for all elements  255 , users, and sectors.  
         [0090]     Following the splitter  865 , filters  870 , such as bandpass filters, filter the composite signals to produce the results for the fifth step  825 . The fifth step  825  includes a respective weight and signal for a given element in the antenna array. Thus, the following equation is provided in the fifth step  825 : for user j, Σi(Wi*Weightj,i*TxSignalj).  
         [0091]     The result of the fifth step  825  is modulated with codes from the Walsh code generator  320  by the modulator  330 . The Walsh code generator  320  is synchronized with and provides the same Walsh codes as the Walsh code generator employed by the weighted Walsh code generator  845  in each of the transmitter modules  835 .  
         [0092]     The output from the modulators  330  is the composite transmission signal of the sixth step  830  to be radiated by the respective antenna element  255 . For the N&#39;th element, the composite transmission signal, CompositeTxSignal(N)=ΣjTxSignalj,N, where TxSignalj,N=WeightN*TxSignalj. In other words, by modulating the coded composite signal to be transmitted by the coded N&#39;th Walsh code, only the weighted transmission signal to be transmitted by the N&#39;th element of the antenna array remains, as described in reference to  FIG. 7 .  
         [0093]     A base station employing the-principles of the present invention just described allows a significantly lower interference level between users in a multi-user, multi-path environment. Further, the base station allows a higher number of users or users at a higher data rate to occupy the-same cell and spectrum while at the same time reducing (i) the cost of a sectored cellular system, and (ii) the cost of a beam forming system. Adding the subscriber antenna array allows a “virtual point-to-point RF connection” with very high data rate/SNR and liability. When combined with a “non-orthogonal BTS code overlay”, additional users may be served.  
         [0094]     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.