MXPA99007160A - Method for frequency division duplex communications - Google Patents

Abstract

The high quality PCS communications are enabled in environments where adjacent PCS service bands operate with out-of-band harmonics that would otherwise interfere with the system's operation. The highly bandwidth-efficient communications method combines a form of time division duplex (TDD), frequency division duplex (FDD), time division multiple access (TDMA), orthogonal frequency division multiplexing (OFDM), spatial diversity, and polarization diversity in various unique combinations. The method provides excellent fade resistance. The method enables changing a user's available bandwidth on demand by assigning additional TDMA slots during the user's session.

Description

METHOD FOR DUPLEX COMMUNICATIONS BY FREQUENCY DIVISION Background of the Invention Field of the Invention This invention relates to improvements to communication systems and methods in a wireless frequency division duplex communications system.

Description of the Related Art Wireless communication systems, such as cellular and personal communication systems, operate on limited spectral bandwidths. They must make highly efficient use of scarce bandwidth resources to provide good service to a large population of users. Examples of such communication systems that deal with high user demands and scarce bandwidth resources are wireless communication systems, such as cellular and personal communication systems. Several techniques have been suggested for such systems to increase the efficiency of the bandwidth, the amount of information that can be transmitted with a given spectral bandwidth. Many of these REF: 30831 techniques involve reusing the same communication resources for multiple users while maintaining the identity of each user's message. These techniques are known generically as multiple access protocols. These multiple access protocols include Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Space Division Multiple Access (SDMA), and Frequency Division Multiple Access (FDMA). The technical foundations of these multiple access protocols are discussed in Rappaport's recent book entitled "Principles and Practice of Wireless Communications", Prentice Hall 1996. The Time Division Multiple Access (TDMA) protocol sends information from a multiplicity of users over a frequency bandwidth signed multiplexing by time division the information of the different users. In this multiplexing scheme, specific time intervals are assigned to specific users. The knowledge of the time interval during which any specific information is transmitted allows the separation and reconstruction of each user message at the receiving end of the communication channel. The Code Division Multiple Access (CDMA) protocol uses a unique code to distinguish each user's data signal from another user's data signals. The knowledge of the unique code with which any specific information is transmitted allows the separation and reconstruction of each user message at the receiving end of the communication channel. There are four types of CDMA protocols classified by modulation: direct sequence (or pseudo noise), frequency hopping, time hopping and hybrid systems. The technical foundations for CDMA protocols are discussed in Prasad's recent book entitled "CDMA for Wireless Personal Communications," Artech House, 1996. The Direct Sequence CDMA (DS-CDMA) protocol broadcasts a user's data signal over a broad portion of the frequency spectrum by modulating the data signal with a public code signal that is of a bandwidth greater than that of the data signal. The frequency of the code signal is chosen to be much greater than the frequency of the data signal. The data signal is modulated directly by the code signal and the resulting encoded data signal models a single broadband carrier continuously covering a wide frequency range. After the transmission of the carrier signal modulated by DS-CDMA, the receiver uses a locally generated version of the user's unique code signal to demodulate the received signal and obtain a reconstructed data signal. The receiver is thus able to extract the user's data signal from a modulated carrier that carries many other user data signals. The Extended Frequency Hopping Spectrum (FHSS) protocol uses a unique code to change a value of the narrowband carrier frequency for successive bursts of the user's data signal. The value of the carrier frequency varies over time over a wide range of the frequency spectrum according to the unique code. The term Extended Spectrum Multiple Access (SSMA) is also used for CDMA protocols such as DS-CDMA and FHSS that use a relatively wide frequency range over which a relatively narrow band data signal is distributed. The term CDMA Time Jump protocol (TH-CDMA) uses a single carrier frequency, of narrow bandwidth, to send bursts of user data at intervals determined by the user's unique code. Hybrid CDMA systems include all CDMA systems that employ a combination of two or more CDMA protocols, such as direct sequence / frequency hopping (DS / FH), direct sequence / time hopping (DS / TH), hopping frequency / time hopping (FH / TH), and direct sequence / frequency hopping / time hopping (DS / FH / TH).

The Space Division Multiple Access (SDMA) transmission protocol forms directed energy beams whose radiation patterns do not overlap spatially with each other, to communicate with users in different places. An adaptive antenna array can be directed in in-phase patterns to simultaneously direct energy in the direction of the selected receivers. With such a transmission technique, the other multiplexing schemes can be reused in each of the separately directed beams. For example, the specific codes used in the CDMA can be transmitted in two different beams. Consequently, if the beams do not overlap each other, the same code can be assigned to different users as long as they do not receive the same beam. The Multiple Access protocol by Division of Frequency (FDMA) serves a multiplicity of users over a frequency band dedicated to particular frequency intervals to specific users, that is, by multiplexing by frequency division the information associated with the different users. The knowledge of the frequency range in any specific information resides and allows the reconstruction of each user information at the receiving end of the communication channel. Orthogonal Frequency Division Multiplexing (OFDM) solves a problem addressed, for example, when signals are transmitted in the form of pulses in an FDMA format. In accordance with well-known principles in the communication sciences, the limited time duration of such signals inherently employs the bandwidth of the signal in the frequency space. Consequently, different frequency channels can overlap significantly, making the use of frequency fail as a parameter that identifies the user, the principle on which the FDMA is based. However, the information in the form of pulses that is transmitted over specific frequencies can be separated, according to the principles of the OFDM, despite the fact that the frequency channels overlap due to the limited time duration of the signals . The OFDM requires a specific relationship between the data rate and the carrier frequencies. Specifically, the frequency band of the local signal is divided into N frequency subchannels, each of which has the same data rate 1 / T. These data streams are then multiplexed over a multiplicity of carriers that are separated by frequency by 1 / T. The multiplexing of signals under these constraints results in each carrier having a frequency response that has zeros in multiples in 1 / T. Therefore, there is no interference between the different bearer channels, despite the fact that the channels overlap each other due to the enlargement associated with the data rate. OFDM is explained, for example, by Chang in Bell Sys. Tech. Jou., Vol. 45, pp. 1775-1796, December 1996, and in U.S. Patent No. 4,488,445. The Parallel Data Transmission is a technique related to the FDMA. It is also known as Multiple Tone Transmission (MT), Discrete Multiple Tone Transmission (DMT) or Multiple Carrier Transmission (MCT). Parallel Data Transmission has significant calculation advantages over simple FDMA. In this technique, each user information is divided and transmitted on the different frequencies, or "tones", instead of on a single frequency, as in the standard FDMA. In one example of this technique, the input data at NF bits per second is grouped into blocks of N bits at a data rate of F bits per second. Then N carriers or "tones" are used to transmit those bits, each carrier transmits F bits per second. The carriers can be separated according to the principles of the OFDM. Both the phase and the amplitude of the carrier can be varied to represent the signal in the multiple tone transmission. In consecuense, multiple tone transmission can be implemented with M-Aryan digital modulation schemes. In an M-Aryan modulation scheme, two or more bits are grouped together to form symbols and one of the possible M signals is transmitted during each symbol period. Examples of M-ary digital modulation schemes include Phase Displacement Modulation (PSK), Frequency Shift Modulation (FSK), and Quadrature Amplitude Modulation (QAM). In the QAM a signal is represented by the phase and amplitude of a carrier wave. In the higher order QAM, a multitude of points can be distinguished on an amplitude / phase graph. For example, in a 64-ary QAM, 64 such points can be distinguished. Since six bits of zeros and ones can take 64 different combinations, a six-bit sequence of data symbols can for example be modulated on a carrier in the 64-ary QAM by transmitting only a fixed value of phase and amplitude, of the possible 64 of such sets. It has been suggested to combine some of the previous temporal and spectral multiplexing techniques. For example, in US Pat. No. 5,260., 967, issued to Schilling, the combination of TDMA and CDMA is described. In U.S. Patent 5,291,475, issued to Bruc ert, and in U.S. Patent 5,319,634 issued to Bartholomew, the combination of TDMA, FDMA and CDMA is suggested. Other suggestions have been made to combine several temporal and spectral multiple access techniques with spatial multiple access techniques. For example, U.S. Patent 5,515,378, filed December 12, 1991, Roy suggests "separating multiple messages in the same frequency, code or time channel using the fact that they are in different spatial channels". Roy suggests the specific application of this technique for mobile cellular communications using an "antenna array". Similar suggestions have been made by Swales et al., In the IEEE Trans. Veh. Technol. Vol. 39. No. 1 February 1990, and by Davies et. Al., In A.T.R., Vol. 22, No. 1, 1988 and in Telecom Australia, Rev. Act., 1985/86 pp. 41-43. Gardner and Schell suggest the use of communication channels that are "spectrally disarticulated" in conjunction with "spatially separable" radiation patterns in U.S. Patent 5,260,968, filed June 23, 1992. The radiation patterns are determined by restoring the properties of " autocoherence "of the signal using an adaptive antenna array. "[A] adaptive antenna array in a base station is used in conjunction with signal processing through the restoration of auto-coherence to separate temporally and spectrally superimposed signals from users arriving from different specific locations." See the Summary of the Invention. In this patent, however, adaptive analysis and restoration of self-coherence is used only to determine the optimal beam pattern; "... [are used] ... conventional spectral filters ... to separate spatially inseparable filters". inters suggests the "adaptive array processing" in which "[t] he frequency domain data of a plurality of antennas ... combine for channel separation and time domain conversion for demodulation", in U.S. Patent 5,481,570, filed October 20, 1993. Column 1 lines 66-67 and Column 2, lines 14-16. Agee has shown that "the use of an antenna arrangement of multiple antenna of M elements in the base station of any communication network can increase the reuse of the frequency of the network in the factor of M and generally extend the range of SINR of input required for proper demodulation ,, .. " ("Wireless Personal Communications: Trends and Challenges ", Rappaport, Oerner and Reed, editors, Kluwer Academic Publishers, 1994, pp. 69-80, on page 69. see also, Proc. Virginia Tech. Third Symposium on Wireless Personal Communications, June 1993, p. 15-1 to 15-12). Gardner and Schell also suggest in U.S. Patent 5,260,968, filed on June 23, 1992, "multiplexing by time division the signal from the base station and the users" ... "[p] to use the same frequency for duplex communications. .. "" [T] he reception at the base station of all mobile units is temporarily separated from the base station transmission to all mobile units. " Column 5, lines 44ff. In a similar lane, US Pat. No. 4,383,332 discloses a multi-element adaptive antenna array SDMA system, wireless, where all the processing of the required adaptive signal is performed in the baseband at the base station through the use of "time division retransmission techniques". Fazel, "Rejection of Narrowband Interference in Extended Spectrum Communications of Orthogonal Multiple Carrier", Record, 1994 Third Annual Conference on Universal Personal Communications, IEEE, 1994, pp. 46-50 describes a transmission scheme based on the extended spectrum and combined OFDM. A plurality of subcarrier frequencies have components of the extended vector assigned to them to provide frequency diversity at the receiving site. The scheme uses the frequency domain analysis to estimate the interference, which is used to weight each of the subcarriers received before the broadcast. This results in the interruption of those subcarriers that contain the interference.

Despite the prior art suggestions of combining certain multiple access protocols to improve bandwidth efficiency, there has been little success in the implementation of such combinations. It becomes more difficult to calculate the optimal operating parameters as more protocols are combined. The implementation of networks that combine multiple access protocols becomes more complex and expensive. Consequently, the implementation of communications with high bandwidth efficiency using a combination of multiple access protocols remains a challenge.

Brief Description of the Invention The invention allows high-quality PCS communications in environments where the adjacent PCS service bands operate with out-of-band harmonics that would otherwise interfere with the operation of the system. The high bandwidth efficiency communications method combines a form of time division duplex (TDD) access, frequency division duplex (FDD), time division multiplex (TDMA), orthogonal frequency division multiplexing (OFDM), spatial diversity, and polarization diversity in several unique combinations. The invention provides excellent fading resistance. The invention allows to change an available bandwidth to the user on request by assigning additional TDMA intervals during the user's session. In one embodiment of the invention, TDD, FDD, TDMA, and OFDM are combined to allow a base station to communicate efficiently with many remote stations. The method includes the step of receiving from the base station a first incoming wireless signal comprising a plurality of frequency / discrete first tones that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of a first remote station during a first time division multiple access (TDMA) interval. The method then includes the step of receiving from the base station a second incoming wireless signal comprising a plurality of second discrete frequency tones. which are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station during the first time division multiple access (TDMA) interval. The first and second stations accordingly have different sets of discrete frequency tones that are multiplexed by orthogonal frequency division. The method includes the step of receiving in the base station a third incoming wireless signal comprising a plurality of discrete first-pitch frequencies that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a third remote unit during a second time division multiple access (TDMA) interval. The first and third stations are consequently multiplexed by time division sharing the same set of discrete frequency tones in the different TDMA intervals. The method then includes the step of receiving in the base station a fourth incoming wireless signal comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a fourth remote station. during the second time division multiple access (TDMA) interval. The second and fourth stations are accordingly multiplexed by time division sharing the same set of discrete frequency tones in the different TDMA intervals. The method then includes the step of transmitting to the base station the first outgoing wired signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station during the third time division multiple access (TDMA) interval. The first remote station and the base station are accordingly duplexed by time division (TDD) by transmitting their respective signals at different TDMA intervals. further, the first remote station and the base station are consequently duplexed by frequency division (FDD) transmitting their respective signals on different sets of discrete frequency tones in different frequency bands. The method then includes the step of transmitting to the base station the second outgoing wireless signal comprising a plurality of quarter discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station during the third time division multiple access interval (TDMA). The second remote station and the base station are accordingly duplexed by time division (TDD) by transmitting their respective signals at different TDMA intervals. In addition, the second remote station and the base station are accordingly duplexed by frequency division (FDD) by transmitting their respective signals on different sets of discrete frequency tones in different frequency bands. The method then includes the step of transmitting to the base station the third outgoing wireless signal comprising the plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the third remote station during a fourth interval of multiple access by division of time (TDMA). The third remote station and the base station are accordingly duplexed by time division (TDD) by transmitting their respective signals at different TDMA intervals. In addition, the third remote station and the base station are accordingly duplexed by frequency division (FDD) by transmitting their respective signals on different sets of discrete frequency tones in different frequency bands. The method then includes the step of transmitting to the base station the fourth outgoing wireless signal comprising the plurality of discrete frequency quarter tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the fourth remote station during the fourth time division multiple access interval (TDMA). The fourth remote station and the base station are accordingly duplexed by time division (TDD) transmitting their respective signals at different TDMA intervals. In addition, the fourth remote station and the base station are accordingly duplexed by frequency division (FDD) by transmitting their respective signals on different sets of discrete frequency tones in different frequency bands. In another embodiment of the invention, TDD, FDD, TDMA, OFDM and space diversity are combined to allow a base station to communicate efficiently with many remote stations. This is possible due to the multi-element antenna arrangement in the base station that is controlled by agglutinating and propagating weights. The propagation of weights allows the base station to direct the signals it transmits to remote stations that have a sufficient geographical separation from each other. The agglutination of weights allows the base station to direct the sensitivity received from the base station to the signal sources transmitted by remote stations that have a sufficient geographical separation from each other. The method includes the step of receiving in the base station a first incoming wireless signal comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band from a first remote station in a first geographic place during a first time division multiple access (TDMA) interval. The method includes the step of receiving in the base station a second incoming wireless signal comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station in a second geographical location during the first time division multiple access (TDMA) interval. The method then includes the step to spatially group the first and second incoming signals received at the base station using spatial weights. Spatial diversity is provided because the pooled weights allow the base station to direct the reception sensitivity of the base station to the first remote station and the second remote station, respectively. Finally, the method performs the spatial dispersion step of first and second outgoing wireless signals at the base station using the spatial dispersion of the weights. The method then includes the step of transmitting to the base station the first outgoing wireless signal comprising a plurality of third discrete frequency tones which are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station. in the first geographical place during the third time division multiple access interval (TDMA). The method then includes the step of transmitting in the base station the second outgoing wireless signal comprising a plurality of third discrete frequency tones which are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station. in the second geographical place during the third time division multiple access interval (TDMA). The spatial diversity is provided because the scattering of the weights allows the base station to direct the signals it transmits to the first and second remote stations, respectively. In another embodiment of the invention, TDD, FDD, TDMA, OFDM and polarization diversity are combined to allow a base station to communicate efficiently with many remote stations. This is possible because the antenna in the base station and the antennas in the remote stations are designed to distinguish orthogonally polarized signals. The signals exchanged between the base station and a first remote station are polarized in one direction, the signals exchanged between the base station and a second remote station are biased in an orthogonal direction. The method includes the step of receiving in the base station a first incoming wireless signal polarized in a first polarization direction comprising a plurality of first discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of a first remote station during a first time division multiple access (TDMA) interval. The method then includes the step of receiving in the base station a second incoming wireless signal polarized in a second polarization direction comprising a plurality of first discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first band. frequency of a second remote station during the first time division multiple access (TDMA) interval. The method then includes the step distinguishing the first and second incoming signals received at the base station by detecting the first and second polarization directions. The polarization diversity is provided because the signals exchanged between the base station and the first remote station are polarized in one direction, and the signals exchanged between the base station and the second remote station are polarized in an orthogonal direction. Finally, the method includes the step of forming a first and second outgoing wireless signals in the base station by polarizing them in a first and second polarization directions, respectively. The method then includes the step of transmitting in the base station the first outgoing wireless signal polarized in a first polarization direction comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station in the first geographic location during a third time division multiple access (TDMA) interval. The method then includes the step of transmitting in the base station the second outgoing wireless signal polarized in the second polarization direction comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second band. frequency to the second remote station in the second geographical location during the third time division multiple access (TDMA) interval. Polarization diversity is provided because the signals exchanged between the base station and the first remote station are polarized in one direction, and the signals exchanged between the base station and the second remote station are biased in an orthogonal direction. In yet another embodiment of the invention, TDD, FDD, TDMA, OFDM, spatial diversity, and polarization diversity are combined to allow a base station to communicate efficiently with many remote stations. The resulting invention makes highly efficient use of scarce bandwidth resources to provide a good service to a large population of users. Currently, the invention has advantageous applications in the field of wireless communications, such as cellular communications or personal communications, where bandwidth is scarce compared to the number of users and their needs. Such applications can be made in mobile, fixed or minimally mobile systems. However, the invention can be applied advantageously to other communication systems, not wireless, too. " Brief Description of the Drawings In the drawings: Figure 1 is an architectural diagram of the PWAN FDD system, which includes the remote stations that communicate with a base station. Figure 1.1 is a diagram of an Organization of PWAN Air Link RF Band. Figure 1.2 is a diagram of Physical Channels. Figure 1.3 is a diagram of a PWAN Physical Layer Frame Structure. Figure 1.4 is a diagram of the Details of the Parameters of the TDMA Interval. Figure 1.5 is a diagram of a data channel of 64 kbit / s A PWAN. Figure 1.6 is a diagram of the Functional Block Diagram of the Base transmitter for a single traffic channel in 16 QAM mode at a rate of 3/4. Figure 1.7 is a diagram of the block diagram for the CLC / BRC Base transmissions.

Figure 1.8 is a plot diagram of the map encoded in gray for the QPSK modulation on the CLC / BRC channel. Figure 1.9 is a diagram of the demultiplexing of a CLC / BRC message into two consequent TDMA frames. Figure 1.10 is a diagram of the Functional Block Diagram of the Base receiver for a single traffic channel in 16 QAM mode at a rate of 3/4. Figure 1.11 is a diagram of the Functional Block Diagram of the Base receiver for a CAC. Figure 1.12 is a diagram of the Functional Block Diagram of the RU transmitter for a single traffic channel in 16 QAM mode at a rate of 3/4. Figure 1.13 is a diagram of the block diagram for RU CAC transmissions. Figure 1.14 is a diagram of the demultiplexing of a CAC message on two consequent TDMA frames. Figure 1.15 is a diagram of the Functional Block Diagram of the RU receiver for a single traffic channel in 16 QAM mode at a rate of 3/4. Figure 1.16 is a diagram of the baseband representation of the RU CLC / BRC receiver. Figure 2.1 is a diagram of the Functional Block Diagram of the Base transmitter for a single traffic channel in 16 QAM mode at a rate of 3/4.

Figure 2.2 is a diagram of the Functional Block Diagram of the Base receiver for a single traffic channel in 16 QAM mode at a rate of 3/4. Figure 3.1 is a diagram of the beam pattern and its effect on the RSSI RU. Figure 3.2 is a diagram of the direct beam pattern altered to accommodate the incoming RU. Figure 4.1 is a diagram of the Processing Diagram. Figure 4.2 is a diagram of the Signals as observed in the Base Station. Figure 4.3 is a Delay Compensation diagram in the action.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGURE 1 is an architectural diagram of the personal frequency access network (PWAN) duplex frequency division (FDD) network system according to the invention. The system employs the method of the invention which combines time division duplexing (TDD) frequency division duplexing (FDD), time division multiple access (TDMA), orthogonal frequency division multiplexing (OFDM), spatial diversity , and polarization diversity in several unique combinations.

Figure 1 provides an overview of how the invention combines TDD, FDD, TDMA, and OFDM to allow the base station Z to communicate efficiently with many remote stations U, V, W, and X. The base station Z receives a first wireless input signal 10 comprising a plurality of discrete frequency first tones F2 that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of the first remote station U during a first time division multiple access interval (TDMA). The organization of the TDMA intervals is shown in Figure 1.5, which is discussed in detail later. The base station Z then receives a second incoming wireless signal 12 comprising a plurality of second discrete frequency tones F4 which are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station W during the first Time division multiple access interval (TDMA). The first and second stations U and W accordingly have different sets of discrete frequency tones F2 and F4, which are multiplexed by orthogonal frequency division. The base station Z in Figure 1 receives a third incoming wireless signal 14 comprising a plurality of the first discrete frequency tones F2 that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a third remote station V during a second time division multiple access (TDMA) interval: The first and second TDMA ranges are part of the same TDMA frame, as shown in Figure 1.5. The first and third stations U and V are accordingly multiplexed by time division by sharing the same set of discrete frequency tones F2 at different TDMA intervals. The base station Z in Figure 1 receives a fourth incoming wireless signal 16, comprising a plurality of second discrete frequency tones F4, which are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a fourth station remote X during the second time division multiple access (TDMA) interval. The second and fourth stations W and X are accordingly multiplexed by timeshare division to the same set of discrete frequency tones F4 at different TDMA intervals. The base station Z in Figure 1 transmits the first outgoing wireless signal 18 comprising a plurality of discrete frequency third tones Fl that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station U during the third time division multiple access (TDMA) interval. The first remote station U and the base station Z are accordingly duplexed by time division (TDD) transmitting their respective signals 10 and 18 at different TDMA intervals. The first, second, third and fourth TDMA intervals occur in time mutually different, as shown in Figure 1.5. In addition, the first remote station U and the base station Z are accordingly duplexed by frequency division (FDD) by transmitting their respective signals 10 and 18 on different sets of discrete frequency tones F2 and Fl in different frequency bands. The base station Z in Figure 1 transmits the second outgoing wireless signal 20 comprising a plurality of quarter discrete frequency tones F3, which are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station W during the third time division multiple access (TDMA) interval. The second remote station W and the base station Z, accordingly, are duplexed by time division (TDD) transmitting their respective signals 12 and 20 at different TDMA intervals. In addition, the second remote station W and the base station Z are, accordingly, duplexed by frequency division (FDD) transmitting their respective signals 12 and 20 on different sets of discrete frequency tones F4 and F3 in different frequency bands.

The base station Z in Figure 1 transmits the third wireless output signal 22, which comprises the plurality of discrete frequency third tones Fl that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the third station remote V during the fourth time division multiple access interval (TDMA). The third remote station V and the base station Z, accordingly, are duplexed by time division (TDD) transmitting their respective signals 14 and 22 at different TDMA intervals. In addition, the third remote station V and the base station Z are, accordingly, duplexed by frequency division (FDD) transmitting their respective signals 14 and 22 on different sets of discrete frequency tones F2 and Fl in different frequency bands. The base station Z in Figure 1 transmits the fourth wireless output signal 24, which comprises the plurality of fourth discrete frequency tones F3 that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the fourth station remote X during the fourth time division multiple access interval (TDMA). The fourth remote station X and the base station Z, accordingly, are duplexed by time division (TDD) transmitting their respective signals 16 and 24 at different TDMA intervals. In addition, the fourth remote station X and the base station Z are, accordingly, duplexed by frequency division (FDD) transmitting their respective signals 16 and 24 on different sets of discrete frequency tones F4 and F3 in different frequency bands. Figure 1 shows another embodiment of the invention, where TDD, FDD, TDMA, OFDM and space diversity are combined to allow the base station to efficiently communicate with many remote stations. This is possible due to the arrangement of multiple element antenna A, B, C and D in the base station Z which is controlled by grouping and dispersing weights. The scattering of weights allows the base station Z to direct the signal that it transmits to the remote stations U and V that have a sufficient geographical separation from each other. Grouping weights allows the base station Z to direct the sensitivity of the reception of the base station to the sources of the signals transmitted by the remote stations U and V that have a sufficient geographical separation from each other. To illustrate the effectiveness of spatial diversity in this modality, the remote stations U and V share the same discrete frequency tones Fl and F2 and the same TDMA interval. The base station Z in Figure 1 receives a first incoming wireless signal 10 comprising a plurality of first discrete frequency tones F2 that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the first remote station U to a first geographic location during a first time division multiple access (TDMA) interval. The base station Z in Figure 1 receives a second incoming wireless signal 14 comprising a plurality of first discrete frequency tones F2 that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the second remote station V in a second geographic location during the same first time division multiple access (TDMA) interval. The base station Z in Figure 1, spatially propagates the first and second incoming signals 10 and 14 received at the station Z using the spatial weights grouping. The spatial diversity is provided because the weight grouping allows the base station Z to direct the reception sensitivity of the base station to the first remote station U and the second remote station V, respectively. Finally, the base station Z in Figure 1, spatially propagates first and second outgoing wireless signals 18 and 22 at the base station using the spatial propagation of weights. Then, the base station Z in Figure 1, transmits the first outgoing wireless signal 18 comprising a plurality of discrete frequency third tones Fl that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first space station remote U at the first geographical location during the third time division multiple access (TDMA) interval. The base station Z in Figure 1 transmits the second outgoing wireless signal 22 comprising a plurality of discrete frequency third tones Fl that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station V in the second geographical location during the same third time division multiple access (TDMA) interval. The spatial diversity is provided because the weight propagation allows the base station Z to direct the signals it transmits to the first and second remote stations U and V, respectively. Figure 1 shows yet another embodiment of the invention, where the TDD, FDD, TDMA, OFDM and space diversity combine to allow the base station Z to communicate efficiently with many remote stations U, V, W and X. This is possible because the antenna A, B, C or D in the base station Z and the antennas in the remote stations U, V, W and X are designed to distinguish orthogonally polarized signals. The signals exchanged between the base station Z and a first remote station U are polarized in one direction, and the signals exchanged between the base station Z and a second remote station V, are biased in an orthogonal direction. To illustrate the effectiveness of the polarization diversity in this mode, the remote stations U and V share the same discrete frequency tones Fl and F2 and the same TDMA interval. The base station Z in Figure 1 receives a first incoming wireless signal 10 polarized in a first polarization direction comprising a plurality of first discrete frequency tones F2 that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band. frequency of the first remote station U during the first time division multiple access (TDMA) interval. The base station Z in Figure 1 receives a second incoming wireless signal 14 polarized in a second polarization direction comprising a plurality of first discrete frequency tones F2 that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band. frequency of a second remote station V during the first time division multiple access (TDMA) interval. The base station Z in Figure 1 distinguishes the first and second incoming signals 10 and 14 received at the base station, detecting the first and second polarization directions. Polarization diversity is provided because the signals exchanged between the base station Z and the first remote station U are polarized in one direction, and the signals exchanged between the base station Z and the second remote station V, are polarized in one direction orthogonal.

Finally, the base station Z in Figure 1, forms a first and second outgoing wireless signals 18 and 22 at the base station by polarizing them in the first and second polarization directions, respectively. Next, the base station Z 'in Figure 1 transmits the first outgoing wireless signal 18 polarized in the first polarization direction comprising a plurality of discrete frequency third tones Fl that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band of the first remote station U at the first geographical location during a third time division multiple access (TDMA) interval. Next, the base station Z in Figure 1 transmits the second outgoing wireless signal 22 polarized in the second polarization direction comprising a plurality of discrete frequency third tones Fl that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station V in the second geographical location during the third time division multiple access (TDMA) interval. Polarization diversity is provided because the signals exchanged between the base station Z and the first remote station U are polarized in one direction, and the signals exchanged between the base station Z and the second remote station V, are polarized in one direction orthogonal. In a still further embodiment of the invention, the TDD, FDD, TDMA, OFDM, spatial diversity and polarization diversity combine to allow a base station Z to communicate efficiently with many remote stations U, V, W and X. The resulting invention It makes highly efficient use of scarce bandwidth resources to provide a good service to a large population of users. The PWAN system has a total of 3200 discrete tones (carriers) equally spaced at 10 MHZ of available bandwidth in the range of 1850 to 1990 MHZ. The separation between the tones is 3.125 kHz. The total set of tones is numbered consecutively from 0 to 3199, starting from the lowest frequency tone. The tones are used to carry traffic messages and air messages between the base station and the plurality of remote units. In addition, the PWAN system uses aerial tones to establish synchronization and to pass control information between the base station and the remote units. A Common Link Channel (CLC) is used by the base to transmit control information to remote units. A Common Access Channel (CAC) is used to transmit messages from the remote unit to the base. There is a grouping of tones assigned to each channel. These air channels are used in common by all remote units when they are exchanging control messages with the base station. The selected tones within each set of tones are designated as pilots distributed across the frequency band. Pilot tones carry known data patterns to allow accurate channel estimation. The series of pilot tones, which have known amplitudes and phases, have a known level and are spaced approximately 30 KHz to provide an accurate representation of the channel response (i.e., the amplitude and phase distortion introduced by the channel characteristics). communication) over the entire transmission band.

Section 1 Physical Layer PWAN FDD 1. 1 Overview The PWAN FDD system uses a TDMA structure to provide several data rates, and to allow a hybrid FDD / TDD technique at the remote station (RU). The FDD is used in the sense that the base and the RU transmit and receive on two separate bands, and the TDD is used to indicate that for a given connection, both the base and the RU transmit and receive on different TDMA intervals. This has no effect on the total capacity of the system, and is only a measure to simplify the design of the RU; that is, to ensure that a duplexer is not needed in the UK. 1. 2 Frequency Definitions The total bandwidth allocation for the air link of the PWAN networks is 10 MHZ in the PCS spectrum, which is the range of 1850 to 1990 MHZ. The total bandwidth is divided into two bands of 5 MHZ, called Lower RF Band and Upper RF Band. The separation between the lowest frequency in the Lower RF Band and the frequency in the Upper RF Band (DF) is 80 MHz. The base frequency (fbase) for the PWAN network is defined at the lowest frequency of the Lower RF Band, which depends on the specific PCS frequency band. As shown in Figure 1.1, the PWAN frequency assignment consists of a higher frequency band and a lower frequency band. There are a total of 1600 tones (carriers) equally separated in each of the 5 MHZ of the available bandwidth. The separation between the tones is 3.125 kHz. The total set of tones were numbered consecutively from 0 to 3199 starting from the lowest frequency tone. Ti is the frequency of the i th tone: + i. ? F 0 < i < 1599 + - + i. ? F 1600 < i < 3199 where fbase is the base frequency, Df is 3.125 kHz, and DF is 80 MHZ. Equivalently, the relationship can be expressed as: -base + (i + 1/2) -3.125 kHz 0 < i < 1599 fbase + 80000 + (i + 1/2) '3.125 kHz 1600 < i < 3199 The set of 3200 tones is the Tone Space. The tones in the Pitch Space are used for two functions: carrier data transmission, and aerial data transmission. The tones used for the transmission of the carrier data are the Carrier Tones, and the tones dedicated to the pilot channels are the Air Tones.

Bearer Tones Bearer tones are divided into 160 Channels Physicists which consist of 80 Direct Physical Channels (FPC) and 80 Inverse Physical Channels (RPC). Some of these channels are not available because they must be used as security bands between the PWAN and other services in the neighboring bands. Each of the physical channels contains 18 Tones as shown in Figure 1.2. The mapping of the tones in the i-th FPCi, and the i-th RPCi is shown in Table 1.1 and Table 1.2 respectively.

Aerial Tones Aerial tones are used for the following channels: • Direct Control Channel: FCC • Inverse Control Channel: RCC These channels can use any set of the 160 aerial tones. The following equation shows the mapping of the aerial tones: RCC (i) = T1600 + IOI 0 < and < 159 1. 3 Definitions of Timing and Framing The structure is shown in Figure 1.3. The smallest unit of time shown in this figure is a TDMA interval. 8 TDMA intervals constitute a TDMA frame. 16 TDMA frames make a multicuadro, and 32 multicuadros make a superframe. Frame synchronization is done at the superframe level. The limit of the multicuadro is determined from the limit of the superframe. As shown in Figure 1.4, in each TDMA interval, there is a transmission burst and a protection time. The data is transmitted in each burst using multiple tones. The duration of the burst is Trafaga. A duration period of protection is inserted after each burst. Table 1.3 shows the values of the TDMA interval parameters. 1. 4 Carrier Channel Definitions A PWAN carrier channel uses a single physical channel with 18 tones separated by 3.125 kHz. The bandwidth occupation of a carrier channel is therefore 56.25 kHz.

The bearer channels can be used to transport traffic or control information (access and transmission). PWAN traffic channels can carry between 16 kbit / s to 64 kbit / s of information depending on the number of TDMA slots assigned to them. A PWAN 16 kbit / s traffic channel uses a TDMA interval per TDMA box, a 32 kbit / s channel uses 2 TDMA slots per frame, and a 64 kbit / s channel uses 4 TDMA slots per TDMA box, as shown in Figure 1.5. Figure 1.5 assumes that there is no multiple access by space division. However, it may be possible to support more than one user in a given TDMA interval, if the users are geographically separated and the transceiver can take advantage of that separation to form spatial beams. 1. 5 Transmission Formats 1.5.1 Traffic Channel Modulation Modes To increase the total capacity of the system, and to ensure the viable deployment of the system at various levels of interference, propagation environments, and possible required transmission intervals, the PWAN can use several coded modulation schemes (speeds). Under benign channel conditions, a highly efficient code rate can be used. If conditions worsen, a low speed coded modulation scheme is used. It is especially important to consider the high availability requirements for a wireless local circuit system. As an example, consider the use of a 16 QAM scheme with a speed of 3/4 of efficient bandwidth. Lower speed codes may also be used. 1. 5.2. Base Transmission Format 1.5.2.1 Functional Block Diagram of the Base Transmitter 1.5.2.1.1 Traffic Channels (an example) The Base transmits information to multiple RUs in its cell. This section describes the transmission formats for a 16 kbit / s to 64 kbit / s traffic channel, together with a Link Control Channel (LCC) of 1 kbit / s to 4 kbit / s from the Base to a single RU. The 16 kbit / s link is achieved by assigning a TDMA interval per TDMA frame. The TDMA frame is 3 ms in length, so the effective data rate is 16 kbit / s times the number of TDMA slots per TDMA frame. For higher data rates, the process described in this section is repeated at each applicable TDMA interval. For example, for the 64 kbit / s link, 4 TDMA intervals per frame must be allocated; In this case, the process described here is repeated 4 times within a given TDMA frame. The block diagram for the Base transmitter in Figure 1.6 shows the data processing for a TDMA interval. The Binary Source distributes 48 bits of data in a TDMA interval. The bit conversion block to octal converts the binary sequence into a sequence of 3-bit symbols. The sequence of symbols is converted to a vector of 16 elements. A symbol of the Link Control Channel (LCC) is added to form a vector of 17 elements. The vector is encoded by trellis. The trellis coding starts with the most significant symbol (first element of the vector) and continues sequentially until the last element of the vector (the LCC symbol). The output of the demultiplexer trellis encoder is a vector of 17 elements where each element is a signal within the set of signals of the constellation 16QAM. As is known, the pilot symbol is added to form a vector of 18 elements, with the pilot as the first element of this vector. The resulting vector must be transmitted on 8 different antennas. The elements of the vector are weighted or weighted according to the element of the antenna through which they are transmitted. The description of how these weights can be derived is found in Section 2. The 18 symbols destined for each antenna are then placed in inverted DFT frequency trays. (corresponding to the physical channel) where they are converted to the time domain. The symbols are plotted in tones on the i-th direct physical channel FPCi. The tracing of the symbols of the common link channel (CLC) / transmission channel (BRC) in tones is shown in Table 1-4. The digital samples are converted to analog, the RF converted and sent to the corresponding antenna element (0 to 7) for transmission over air. This process is repeated from the beginning for the next 48 bits of binary data transmitted in the next applicable TDMA interval. Figure 1.6 is a Functional Block Diagram of the Base transmitter for a single traffic channel in 16 QAM mode at a rate of 3/4. 1. 5.2.1.2 CLC / BRC channels The block diagram for CLC / BRC transmissions is shown in Figure 1.7. The generation of the CLC / BRC information is represented by a binary source that generates 72 bits of data each CLC / BRC transmission. The 72-bit sequence is encoded by RS using a shortened Reed Solomon RS code (63, 35) to generate a sequence of 40 RS symbols (or equivalently a 240 bit sequence). The 240-bit sequence is then modulated by quadrature phase shift coding (QPSK) where each two bits are plotted on a point of the constellation according to the Gray map shown in Figure 1.8.

The output of the QPSK modulator is a sequence of 120 symbols (S0-S119). The QPSK symbols are interspersed with 24 pilot symbols (P0-P23), where every 5 data symbols, a pilot is inserted. This results in a sequence of 144 symbols. The sequence is then demultiplexed by time in vectors of 8, 18 elements for transmission over 8 TDMA intervals (in two TDMA frames) as shown in Figure 1.9. A vector of 18 given elements is transmitted on 8 different antennas. The elements of the vector are weighted according to the element of the antenna through which they are transmitted. The description of how these weights can be derived is found in Section 2. The 18 symbols destined for each antenna are then placed in the inverse frequency DFT trays (corresponding to the physical channel) where they are converted to the time domain. The digital samples are converted to analog, the RF converted and sent to the corresponding antenna element (0 to 7) to be transmitted to the air. Table 1.4 shows the stroke of the symbols in tones for the CLC / BRC transmissions in the physical channel. 1. 5.2.2 Functional Block Diagram of the Base Receiver 1.5.2.2.1 Traffic Channels (example) Figure 1.10 shows the block diagram of the Base receiver for a traffic channel. During a given TDMA interval, and in a given physical channel, the Base receives signals on all its 8 antennas. The signals are converted in a descending manner, sampled digitally, and transformed back to the frequency domain using a Discrete Fourier Transform (DFT). For a particular traffic channel, the appropriate tones are selected using a demultiplexer. The tones of all the antennas are then sent to a stitcher. The stitcher weighs all the tones of a given antenna by a given weight which can be calculated as described in Section 2, and then adds all the tones of the different antennas (addition of the vectors of 8, 18 elements). The resulting 18 element vector is then sent to a compensator where each element of the vector is multiplied by a phase correction factor, and the pilot symbol is separated from the sequence. The remaining 17 symbols are sent to the trellis decoder which releases 16 symbols (48 bits) of the traffic data, and 1 symbol (3 bits) of LCC data. This process is repeated from the beginning for the next 48 bits of binary data transmitted in the next applicable TDMA interval. Figure 1.10 is a Functional Block Diagram of the Base receiver for a single traffic channel in 16 QAM mode at a rate of 3/4. 1. 5.2.2.2 Common Access Channels (CAC) Figure 1.11 shows the block diagram of the Base receiver for a CAC. During a given TDMA interval, and on a given physical channel, the Base receives signals on all its 8 antennas. The signals are converted in a descending manner, sampled digitally, and transformed back to the frequency domain using a Discrete Fourier Transform (DFT). For a particular CAC channel, the appropriate tones are selected using a demultiplexer. The tones of all the antennas are then sent to a stitcher. The grouper weighs all the tones of a given antenna by a given weight which can be calculated according to what is described in Section 2, and then adds all the tones of the different antennas (addition of the 8f vectors) 18 elements) . The resulting 18 tones are sent to a compensator where each tone is multiplied by a phase correction factor, and 9 pilot symbols are separated from the sequence. The vector of 9 elements is then demodulated by QPSK. Since each element of the vector is a QPSK symbol that represents two bits of information, the demodulation produces 18 bits of information.

The time multiplexer collects the received symbols in 8 consecutive TDMA intervals to form 144 bits of information encoded by RS, thereby forming a block of 24 RS symbols (each RS symbol is 6 bits long). The block RS is then decoded to produce 12 RS symbols or 72 bits of the original CAC information transmitted from the RU. Figure 1.11 is a Functional Block Diagram of the Base receiver for a CAC. 1. 5.2.3 Functional Block Diagram of the RU Transmitter 1.5.2.3.1 Traffic Channels The RU transmits information to the only Base in its cell. This section describes the transmission formats for a traffic channel of 16 kbit / s to 64 kbit / s, together with a Link Control Channel (LCC) of 1 kbit / s to 4 kbit / s from an RU to its Base. The 16 kbit / s link is achieved by assigning a TDMA interval per frame. For higher data rates, the process described in this section is repeated in each applicable TDMA interval. For example, for the 64 kbit / s link, 4 TDMA intervals per frame need to be allocated. The block diagram for the RU transmitter in Figure 1.12 shows the data processing for a TDMA interval.

The Binary Source distributes 48 bits of data in a TDMA interval. The bit conversion block to octal converts the binary sequence into a sequence of 3-bit symbols. The sequence of symbols is converted into a vector of 16 elements. A symbol of the Link Control Channel (LCC) is then added to form a vector of 17 elements. The vector is encoded by trellis. The output of the trellis encoder is another vector of 17 elements where each element is a signal within the set of signals of the 16QAM constellation. Next, a known pilot symbol is added to form a vector of 18 elements. The 18 elements are placed in the inverted DFT frequency trays (corresponding to the physical channel) where they are converted to the time domain. The digital samples are converted to analog, the RF converted and sent to the antenna for transmission to the air. This process is repeated from the beginning for the next 48 bits of binary data transmitted in the next applicable TDMA interval. Figure 1.12 is a Functional Block Diagram of the RU transmitter for a single traffic channel in 16 QAM mode at a rate of 3/4. 1. 5.2.3.2 Common Access Channels (CAC) The block diagram of the CAC transmissions of the RU is shown in Figure 1.13. The generation of CAC information is represented by a binary source that generates 72 bits of data for each CAC transmission. The 72-bit sequence is coded by RS using a shortened Reed Solomon code RS (63, 35) to generate a sequence of 24 RS symbols (or equivalently a 114-bit sequence). The sequence of 114 bits is modulated by QPSK, where every two bits are plotted on a point of the constellation according to Gray's map. The output of the QPK modulator is therefore a sequence of 72 symbols (S0-S71). The QPSK symbols are exchanged with 72 known pilot symbols (P0-P71), where each data symbol, a pilot is inserted. This results in a sequence of 144 symbols. The sequence is demultiplexed by time in vectors of 8, 18 elements for transmission over 8 TDMA intervals (in two TDMA frames) as shown in Figure 1.14. Table 1.5 The tracing of the symbols on tones for CAC transmissions on the inverse physical channel. During each TDMA interval, the 18 symbols are placed in DFT frequency trays (corresponding to the physical channel) where they are converted to the time domain.

The digital samples are converted to analog, the RF converted and sent to the antenna for transmission to the air. Figure 1.14 shows the demultiplexing of a CAC message on two consequent TDMA frames. 1. 5.2.4 RU Receiver Functional Block Diagram 1.5.2.4.1 Traffic Channels Figure 1.15 shows the block diagram of the RU receiver. During a given TDMA interval, and on a given physical channel, the RU receives a signal on its antenna. The signals are converted in a descending manner, digitally sampled, and transformed back to the frequency domain using a discrete Fourier transform (DTF). For a particular traffic channel, the appropriate tones are selected using a demultiplexer. The 18 tones are sent to a compensator, where each tone is multiplied by a phase correction factor, and the pilot symbol is separated from the sequence. The remaining 17 symbols are sent to the trellis decoder, which distributes 16 symbols (48 bits) of traffic data, and a symbol (3 bits) of the LCC data. Figure 1.15 shows the Functional Block Diagram of the RU receiver for a single traffic channel in 16 QAM mode at a rate of 3/4. 1. 5.2.4.2 Common Link and Transmission Channels (CLC / BRC) Figure 1.16 is a representation of a block diagram of the baseband processing at the CLC / BRC receiver. During a given TDMA interval, on a given physical channel used for CLC / BRC transmission, the RU receives a time domain signal through its antenna. The signal is converted in a descending manner, and digitally sampled and transformed back to the frequency domain using a Discrete Fourier Transform (DFT). The appropriate tones for the CLC / BRC are selected using a demultiplexer. The 18 tones are sent to a compensator, where each tone is multiplied by a phase correction factor, and the 3 pilot symbols are then separated. The remaining 15 elements are demodulated by QPSK. Consequently, the demodulator produces 30 bits of information. The time multiplexer collects data in 8 consecutive TDMA intervals to form 240 bits of information encoded by RS thereby forming a block of 40 RS symbols (each RS symbol is 6 bits long). The block RS is then decoded to produce 12 RS 72-bit symbols of the original CLC / BRC information transmitted from the Base.

Section 2 Spatial Processing PWAN FDD Introduction Spatial processing is incorporated into the PWAN physical layer to provide greater capacity and an improved degree of service. This is achieved through spatial isolation through the reuse of frequency and through the suspension of co-channel interference. In a frequency division duplex (FDD) system where the transmission and reception bands are widely separated in frequency, reciprocity in the channel is not achievable. Therefore, different beam formation strategies are needed in the direct and inverse channels. This section specifically describes those functions that are required to implement spatial processing in the PWAN Base station. Space processing in the Remote Unit is optional and offers potential means of gaining spatial degrees of freedom to further increase capacity. The main functions present in any beam forming system will be described for both the forward and reverse links. They include the application of the weights that form the beam, weight calculation, adaptation and incorporation of the reference pilots. 2. 1 Narrowband Assumption It is primarily important to address one of the main assumptions inherent in any beamforming system; either narrowband or broadband frequency. For the PWAN system, it is assumed that all beam formation is narrowband. It is necessary to define the system as a narrow band in principle to ensure that the frequency responses in different elements of the array match perfectly and that the spatial samples received are sufficiently correlated from one end of the array to the next. The assumption can be examined analytically in the context of observing the time-bandwidth product for the antenna opening of the base station. It can also be tested by observing the mismatch present in the beam pattern through the frequency band of interest. The observation time interval for the opening of an antenna is defined as the time required for a flat waveform to travel completely through the antenna opening. This is a function of the angle of arrival of the signal. The time-bandwidth product observation (TBWP) is the product of the observation interval of the signal bandwidth. For the array to be considered narrowband, the TBWP must be much less than 1 for all arrival angles. A rapid calculation of the TBWP for a linear aperture with a uniform separation of 8 elements should give a limit on this TBWP for the PWAN, since this would be the limiting case over the observation interval for a uniformly separated arrangement. Equation 2.1 and the Equation 2. 2 describe this calculation, where Td is the time interval of observation, BW is the bandwidth of the signal (112.5 kHz), N is the number of elements of the array (8), and c • is the speed of light.

(Eq. 2.1) Td = (Element Separation * sin (arrival angle)) / c) * (Nl) = (2.63e-10) * (8-l) = 1.84e-09 (Eq. 2.2) TBWP = 1.84e-09 * BW = 1.84e-09 * 112.5e03 = 2.07e-04 TBWP = 2.07e-04 «l This calculation was made for the maximum deflected arrival angle of the sight (at the fire end) of 90 degrees for the maximum observation interval. As can be seen from equation 2.1, the TBWP is much smaller than one for the maximum delay (all other angles would be smaller than TBWP), so it maintains the narrowband assumption. This assumption was also investigated for the linear arrangement through simulations with the result that the mismatch in beam patterns over this bandwidth had a negligible mean square error (MSE); validating again the narrowband assumption. 2. 2 Far Field Assumption Another important assumption inherent in the PWAN beamforming system is the far field assumption. This states that all beamforming functions are designed for waveforms received in the far field (> ~ 4 meters) as opposed to near field (< ~ 4 meters). This allows the designer to treat any propagation waveform that collides on the antenna aperture as a flat wave front, thereby implying that the propagation of the signal between two antenna elements can be characterized as a pure delay. It is assumed that the signal has an equal intensity at any point on the flat wave front. 2. 3 Direct Channel On the direct or outgoing channel, from the Base station to the RU, beam formation is used to provide isolation between spatially separated RUs. In the transmission of the Base, beam formation is based on estimates of the arrival direction derived from the received RU transmissions. In the UK receiver, spatial isolation is provided by combining data in the antenna aperture itself for a fixed, continuous beam pattern. 2. 3.1 Base Transmitter A functional representation of a single traffic channel for the base transmitter is presented in Figure 2.1. This section will deal with those components of the Base transmitter that directly implement the spatial processing functions; the shaded Propagator block in Figure 2.1 and the array of the antenna. Figure 2.1 is a Functional Block Diagram of the Base transmitter for a single channel of 16 QAM mode traffic at a rate of 3/4. 2. 3.1.1 Antenna Array The array of the antenna for the base transmitter consists of N sensors that transmit spatially weighted signals from each array element. This arrangement is configured in a hemispherical geometry with a uniform or non-uniform separation of elements. 2. 3.1.2 Application of Weight The formation of the beam in the forward direction is achieved by applying a complex weight matrix, W, composed of vectors of weight that correspond to each user, so that the transmitted signal is reinforced in the direction of the RU desired and attenuated for all other transmission directions. This weight application is described in the following equation: (Eq 2.3) X = WY Equation 2.3 represents a matrix multiplication of the baseband tone data, Y, by the weight matrix, W, to produce the tone data to be modulated and transmitted, X. 2. 3.1.3 Weight Derivation The Propagator block within the transmitter of the Base provides the spatial weights matrix, W, to be applied to the tone data to be transmitted. This matrix can be derived by one of several methods; from independent fixed beam weights of the data derived from the spatial separation of the aperture of the antenna array, in real time, adaptable, the calculation of the statistically optimal beam weights derived from the second order statistics of the data received on the opening of the antenna array, or by receiving any type of weight through an interface from another Base subsystem. Each method of weight derivation involves certain advantages with respect to spatial isolation, rejection of co-channel interference and complexity of system processing. Fixed beam weights, independent of the data, place a computational load in real time over the baseband subsystem, since these weights can be precalculated and tabulated for real-time call based on call. The independent weights of the data provide spatial isolation between the downlink transmissions for spatial division multiple access (SDMA) but, they will not direct nulls for the direct supersion of the co-channel interferences. However, the suppression of these interference factors is inherent in the spatial isolation provided by the ratio of the main lobe to the lateral lobe, but the advantages (spatial resolution and greater attenuation) of the adaptability directing the nulls directly to the co-channel interference are not available. Statistically optimal beamforming weights provide direct suppression of co-channel interference, but require higher processing power and produce greater latency due to convergence times in the calculation of weight. It should also be noted that the FDD systems, the arrival direction estimation (DOA) will not provide the beamformer with accurate estimates of multiple path components due to the independence of the effects of the channel over the wide frequency separation of the direct and reverse or round-trip bands. This implies that the transmitter beamformer will not only be able to simulate the transmissions of the fixed observation line (LOS) of the RUs that interfere. Another significant benefit of this method, however, is the higher resolution of the main beam, thus providing greater spatial resolution over the independent weights of the data. 2. 3.1.4 Weight Update The weight matrix, W, must be updated periodically. This update is required to track the changes in the outbound link channel as well as individual channels that are continuously being deactivated and activated on that channel. For data-independent weights, channel tracking is not applied and the weight update is based on a per-call basis. For statistically optimal weights, the update interval is based on the adaptation speed derived from the channel statistics (product bandwidth and channel stationarity). 2. 3.1.5 Reference Signal The Base shall transmit reference link maintenance (LMP) pilots to provide a phase reference for coherent demodulation and an estimate of the desired signal for the estimation of the beam formation error. The reference signals are transmitted on the outgoing link and the return link. This allows the Base to make the mid frame error (MSE) measurement to be used in the derivation of an optimal beam formation solution on the return link without depending on the arrival direction estimation. 2. 3.1.6 Estimation of the Arrival Direction The a priori knowledge of the arrival angle for the RU transmitters is required to direct the transmission beams to the desired signals on a call-by-call basis. This information must be gathered through DOA estimation techniques. 2. 3.2 Receiver of the RU The space processing techniques of the base band of the RU perform the spatial processing at the opening of the array to form a continuous beam. 2. 4 Return Channel On the return link, from the RU to the Base, beam formation is used to provide spatially separated UV isolation and to provide co-channel interference suppression. In this connection, the a priori knowledge of the arrival angle of the RU transmissions is not required, rather, the formation of the adaptive beam of the reference signal is used. 2. 4.1 Base Receiver A functional representation of a single traffic channel for the Base receiver is presented in Figure 2.2. This section deals with those components of the Base receiver that directly implement the spatial processing functions; the Shaded Grouping block in Figure 2.2 and the array of the antenna. Figure 2.2 shows the Functional Block Diagram of the Base receiver for a single traffic channel in 16 QAM mode at a rate of 3/4. 2. 4.1.1 Antenna Array The antenna array for the Base receiver consists of N sensors that sample the waveforms that collide over the array aperture in each element of the array. This arrangement is configured in a hemispherical geometry with any uniform or non-uniform element separation. 2. 4.1.2 Weight Application Spatial processing in the reverse direction is achieved by applying a full weight matrix, W, composed of weight vectors that correspond to each user, so that the received signal is reinforced in the direction of the desired RU and attenuated in all other directions. This weight application is described in the following equation: (Eq 2.4) Y = WX Equation 2.4 represents a matrix multiplication of the baseband tone data, X, by the weight matrix, W, to produce the grouped tone data, Y. 2. 4.1.3 Weight Derivation The Grouping block within the Base receiver provides the spatial weights matrix, W, to be applied to the received data. This matrix can be derived by one of several methods; from fixed beam weights independent of the data derived from the spatial separation of the aperture of the antenna array, in real time, adaptive, the calculation of the statistically optimal beam weights derived from the second order statistics received on the antenna fix aperture, or by receiving any type of weight through an interface of another subsystem of the Base. Each method of weight derivation involves certain advantages with respect to spatial isolation, rejection of co-channel interference and complexity of system processing. Fixed beam weights, independent of the data, place the lowest computational weight in real time over the baseband subsystem, since those weights can be precalculated and tabulated to be queried on a per-call basis in real time. The independent weights of the data provide spatial isolation between the uplink transmissions for spatial division multiple access (SDMA) but, they do not direct the nulls for the direct supersion of the co-channel interference. However, the suppression of these interferences is inherent to the spatial isolation provided by the relationship of the main lobe to the lateral lobe, but the advantages (spatial resolution and greater attenuation) of the adaptability directing the nulls directly to the co-channel interference are not available. Statistically optimal beam-forming weights provide direct suppression of co-channel interference, but require - higher processing power and cause greater latency due to convergence times in the calculation of weight. 2. 4.1.4 Weight Update The weight matrix, W, must be updated periodically. This update is required to track the changes in the return link channel as well as the individual links that are being continuously activated and deactivated on the channel. For the independent weights of the data, channel tracking is not applied and the weight update is based on a base per channel. For statistically optimal weights, the update interval is based on the adaptation speed derived from the channel statistics (product bandwidth and channel stationarity). 2. 4.1.5 Estimation of the Arrival Address In the return link, the arrival address is estimated by the set of data received for the application on the outbound link. This information allows the Base to transmit the beamformer to direct the beams to the intended RU and, for statistically optimal weights, zero in the RUs that interfere. For a wireless local circuit system such as the PWAN, it is not necessary to track the arrival angle estimation since the original RUs are fixed in space. As mentioned above, those estimates of the arrival angle have the disadvantage of being independent through the PCS bands and that multiple path effects will not follow. 2. 4.1.6 Reference Pilots The Base shall transmit reference link maintenance pilots (LMPs) to provide a reference of the phase for coherent demodulation and an estimate of the desired signal for the estimation of the beam formation error. The reference signals are transmitted on the outgoing link and the return link. This allows the Base to make a measurement of the mid-frame error (MSE) to be used in the derivation of an optimal solution of beam formation on the return link without depending on the estimation of the direction of arrival. 2. 4.2 RU transmitter The RU base-band space processing techniques perform spatial processing at the array aperture to form a continuous beam.

Section 3 PWAN Channel Assignment Introduction When a traffic channel must be established for an RU, the base must assign a channel over which the RU can satisfy the required degree of service. 3. 1 RU capacity The channel allocation algorithm needs to know information related to the capabilities of each RU active and new. If future equipment operates on different IF bandwidths then the channel allocation algorithm needs to know which one can support each device. In the first generation of PWAN the RUs support an operation bandwidth of 1 MHz. This allows operation on any of 16 channels. When a RU is identified by its RUID the base searches for a database that contains the required information about the RU for the frequency assignment algorithm, for example the frequency (IF), bandwidth (BW), "number of carriers (B) supported, types of supported voice coding, etc. 3. 2 Arrival Address (DOA) Since the system is independent of the SDMA to increase capacity, a very important parameter is the DOA of each RU. The channel allocation algorithm needs to know the DOA of each RU involved in an active call and the DOAs of any new RUs. Initially a channel allocation algorithm could be devised which simply maximizes the separation of the DOA between a new RU and the other active RUs over some number of available sets. However, as the numbers of users in the system increase, there is a need for more information to be incorporated into the channel selection rather than the DOA. There are several candidate algorithms for estimating DOA: • coherent signal-subspace (CSS) with spatial interpolation • SS -DOA • MUSIC • ESPRIT 3. 3 Channel Measurements For the best channel to be chosen, the RUs must make measurements on a number of channels and report the results to the base station for use in selecting the best channel for a RU when a link is established. These measurements include the RSSI and the SINR. Table 3.1 shows roughly the search of how the information of the signal strength indicator of the received signal (RSSI) and the signal to interference ratio (SINR) could be used to assign incoming RU channels. It is clear that the lower RSSI on a better channel would be the candidate since there is little energy directed to that RU on that channel by any base. However, a RU could measure the energy of a lateral lobe of the outgoing antenna pattern as shown in Figure 3.1. From Figure 3.1 it is observed that the incoming RU could be accommodated if the service base altered its beam pattern so that the established RU would direct a null to the incoming RU. Similarly, the beam pattern for the incoming RU could have a zero directed to the established RU. This situation is shown in Figure 3.2. Figure 3.1 shows the pattern of the outbound beam and its effect on the RSSI of the RU.

Figure 3.2 shows the altered beam pattern altered to accommodate the incoming RU. With only RSSI information it is impossible to distinguish between the lateral lobe of the service base beam and the interference of the surrounding bases. To help decide between intercell and intracell energy, the SINR measurements are used. A low SINR value indicates high levels of noise and interference on the channel. A high SINR value indicates a clear signal from the service signal. So for the situation shown in Figure 3.1 the RU would report a significant RSSI with a very high SINR. If the DOA of the incoming RU were sufficiently far from the established RU then there would be enough information to know that the outgoing beam pattern can be angled to accommodate the incoming RU on those channels as shown in Figure 3.2. As a first cut it is observed that the three pieces of data can be combined in a channel candidacy evaluation factor (CAF). The three desirable situations are: large separation in the DOA, small RSSI and high SINR. So an equation to quantify the candidacy of channel n is (Ec 3.1) CAF (n) = fDOA (n) + fRSSI (n) - fSINR (n) (Eq 3.2) fDOA (n) = al (180 - min (* | DOAe (k) - DOAij)) for all k (Ec 3.3) fRSSI (n) = a2 (133 + RSSI (n)) (Ec 3.4) fSINR (n) = a3 (SINRRU (n) + (SINRBase (n)) A lower CAF value indicates a better candidate for that channel. An ideal channel would have a CAF of 0. Equation 3.2 through Equation 3.4, al, a2 and a3 are scale factors for the three terms. The first term of Equation 3.1 evaluates the information from the DOA. The maximum possible separation is 180 degrees. So a greater difference in the DOA will make the first term smaller. The second term of Equation 3.1 evaluates the RSSI measurement. The noise floor of the receiver is -133 dBm. This is the ideal measurement that does not indicate activity on that channel, so any value greater than -133 dBm diverts the CAF away from the ideal. The third term of Equation 3.2 includes the effects of the channel SINR. A large SINRRU value gives a better CAF since it means that the energy observed by the RU is from the service base. Similarly, a higher SINRBase means less interference than the RUs in other cells on that channel.

Example al = al = l, a3 = l / 2 A RU requests a traffic channel from its service cell. Report the following measurements as part of the traffic establishment: RSSI (l) = -95 dBm, SINRRU (l) = 9.3 dB RSSI (2) = -95 dBm, SINRRU (2) = 4.5 dB.

The service base measures the DOA of the incoming RUs as 42 degrees. There is an RU on channel 1 at 127 degrees, and a channel 2 at 133 degrees. Also, SINRBase (1) = 12 dB, and SINRBase (2) = 13 dB.

CAF = (180 - | 127 - 42 |) + (133 - 95) - 0.5 (9.3 + 12) = 122.35 CAF (2) = (180 - | 133 - 42 |) + (133 - 95) - 0.5 (4.5 + 13) = 118.25 The RU measured the same RSSI on both channels. The DOA of the existing RU on channel 1 was slightly better than the DOA of the existing RU on channel 2. The SINR measurement of the base for channel 1 was slightly better than the measurement for channel 2. The measurement that had the biggest difference in this case was the SINR of the UK.

To effectively measure the SINR, the RUs and the base must make sense of whether or not a signal belongs to a given cell. Without any such mechanism a SINR measure would be the same for a signal of a given RSSI level of the service base as it would be for a signal from a neighbor base with the same RSSI value. One way to differentiate signals in different cells is to code the reference pilots on the traffic channels with different phases or sequence of phases that would be derived from the Code of Displacement of the Base Station. 3. 4 Procedure 1. In the idle mode, each RU measures the RSSI and the SINR of each channel that could potentially operate and orders them from the best subjective to the worst subjective. 2. There is a parameter, meas_rpts, which is sent over the transmission channel of each base that establishes how many channel measurements in the RU will be sent to the base when a traffic connection is established. 3. When a traffic connection is to be established, the RU sends the best measures meas_rpts channel to the base on the SCAC channel. 4. The base uses the channel measurements sent by the RU to calculate a CAF for each of the candidate channels in the set sent by the RU. 5. If one or more of the channels is the set that was sent by the RU, it produces an acceptable CAF, then the channel with the best CAF is chosen. 6. If one of the channels in the set that was sent by the RU produces an acceptable CAF then the base requests the next best measurement set meas_rpts of the RU. 7. The base repeats steps 4 through 6 until any acceptable channel is found and is then used or the list of candidate channels is exhausted at the point at which the call is blocked.

Section 4 Synchronization of the PWAN Introduction The synchronization algorithms of the RU and delay compensation of the Base. Both algorithms are intended to achieve synchronization at any time (delay compensation of the Base), or in time and frequency (without the RU). .1 Synchronization of the RU When the remote unit (RU) is initialized and starts receiving transmissions from its Base, the arrival time of the waveform is unknown. Also, the RU Signal Pilots (RSP) will probably not be within the prescribed FFT trays because the Base Oscillator and the RU oscillator are operating at slightly different frequencies. The purpose of the synchronization algorithm is to align the processing window of the RU, or reception gate, with the waveform, and adjust the reference oscillator of the RU (VCXO) to operate at the same frequency as the oscillator of the Base. The synchronization is presented as a two-step process, first, the acquisition of the synchronization waveform must occur in both time and frequency. The UK reception gate is adjusted to contain the majority of the signal power, and the RU VCXO is adjusted to eliminate most of the RU-Base's frequency disparity. Conducting the deviation of the residual frequency to zero and maintaining a deviation of the average frequency from zero requires a robust method of frequency estimation, which operates continuously during the operation of the RU. Once the error of the frequency is eliminated, it is said that the RU was closed by frequency to the base. Keeping the frequency error at zero is the function of the frequency tracking step, which works continuously in the background. The closed phase circuit (PLL) is able to follow the phase that varies with time, immersed in noise, and thus is an effective frequency estimator to track frequency errors of. the RU-Base. In effect, the PLL is the implementation of the optimal probability; that is, maximum, of the estimator of the carrier phase. The only requirement for the algorithm is that the system is based on orthogonal frequency division multiplexing (OFDM), with uniform separation between the tones. 4. 1.1 Required Time for Synchronization The RU synchronization is performed at the time of the initialization of the RU, or whenever synchronization is lost. The time requirements to achieve initial synchronization are not as crucial as for the case when the RU has to establish the frequency closure after the sleep mode. The life of the RU battery is the critical aspect in preserving the resynchronization time to a minimum. The time and bandwidth of the frequency are the resources that determine how much it takes to achieve the closing of the frequency. The effects of the channel and noise must be averaged in the estimation of time delay and frequency deviations; it can be averaged over time or over frequency, to mitigate those effects. There must be a balance between the use of available bandwidth and the time constraints determined by the requirements of the system. 4. 1.2 Implementation of the Synchronization of the RU 4.1.2.1 Synchronization Pilots The proposed synchronization algorithm does not assume a particular model for the configuration of the data channel. That is, it does not assume the trace of a particular tone map of the pilot's waveforms, or the pilots of the RU signal (RSP). The RSPs may comprise the aerial tones of a data channel, be in a separate synchronization channel, or be part of the framing structure of a message. 4. 1.2.2 Functional Description The final objective of the synchronization is to achieve the closing of the time and frequency for data demodulation. The precise alignment of the gate of reception time of the RU with the burst of data, and the closing of frequency of the oscillator of the RU with the Base that is requisite for the orthogonality of the data of the FFT tray, and consequently, for reliable demodulation. The synchronization depends on a multi-step procedure in which approximate adjustments are made in time and frequency, then fine adjustments are made in time and frequency for system specifications. These steps, marked as approximate time alignment, approximate frequency alignment, fine time alignment and frequency tracking, are discussed below. 1. Alignment of Approximate Time. The waveform must be inside the receiver gate for the determination of the RSP in the frequency. The approximate time alignment is achieved with a filter coupled to the waveform of frequency deviation. 2. Alignment of Approximate Frequency. The outputs of a filter bank coupled in the frequency domain produce an approximate estimate of the frequency deviation. The VCXO of the RU is adjusted to bring the RU oscillator within a specific frequency tolerance of the Base Oscillator. 3. Monitoring of Frequency. A closed phase circuit (PLL) directs the deviation of the frequency to zero and continuously adjusts the VCXO of the RU to maintain the average frequency difference at zero. 4. Fine Time Alignment This aligns the waveform with the receiver gate of the RU within the final required accuracy. 4. 1.2.3 Processing Description A high-level block diagram for processing steps is given in Figure 4.1. Figure 4.1 shows the methods used to achieve the objectives of each processing step. Except for the frequency tracking step, uniform filtering is the main tool for the acquisition of time and frequency. The realization of the uniform filter differs in each step, but the concept is identical. The approximate time alignment uses a filter impulse response that is compared to the frequency deviation waveform. The approximate frequency alignment uses a bank of filters to estimate the frequency deviation. The final time alignment step uses a single filter that is tuned to the specified exact frequency. 4. 2. Delay Compensation When a RU is installed, it needs to know when to transmit its signals in relation to the signals received from the Base station, so that its signal arrives at the base station at the same time as the signals from other RUs. The base station measures the difference between the expected arrival time and the actual arrival time of the "RU signals." This then transmits this measured information to the RU so that it can advance or delay the time it sends the information. signals to the base station Figure 4.2 shows the signals that appear on the base station The base station waits to see that the signals of the RU arrive after it transmits its last burst Figure 4.3 shows the signals that appear in the Base and RU Before the RU is compensated, the signals it transmits arrive at the base at a different time than the signals transmitted by the other RUs The Base measures the delay and transmits the measurement to the RU. then set the transmission time to compensate for the delay.The delay compensation can be done after the installation and also set each call.The Delay Compensation calculation routine examines the delay. The average signal is used in the signals used to calculate the delay and if they are above a certain threshold, a delay compensation measurement is made. Figure 4.3 shows the Delay Compensation in the action. 4. 2.1 Description of the Algorithm The delay compensation depends on the measurement of the phase and the pilot tones called delay compensation pilots (DCP). The RU transmits the DCPs to the base station with each DCP having the same phase shift. If the RU has been properly compensated the DCP tones arrive at the base station in phase with each other. If the RU signal is delayed then each of the DCP's tones undergo a phase shift, which is proportional to the frequency of the DCP. The base measures the phase of each DCP and uses the linear regression to adjust the phases to a straight line. The slope of this line is proportional to the delay. The zero slope indicates that the delay compensation is not necessary, while the zero-free slope means that the signal is arriving very early (or late) and the RU needs to delay (or advance) the transmission of its signal. The effects of multiple trajectory and noise will corrupt the measurements of the phase. This can be mitigated by averaging the measurements of the phase over the frequency (over the DCP) and over time (over successive data bursts).

Section 5 Diversity Introduction Diversity is a communication receiver technique that re-exploits the random nature of radio propagation by finding highly uncorrelated signal paths for communication. Diversity decisions are made by the receiver. If one radio path experiences a deep fading, another independent path can have a strong signal. Having more than one path to select, the instantaneous and average signal-to-noise ratios in the receiver can be improved. In the diversity of space, receiving antennas of the base station or multiple remote station are used to provide diversity reception. In the polarization diversity, the horizontal and vertical polarization paths between a remote station and a base station are not correlated. Decorrelation of the signals in each polarization is caused by multiple reflections in the channel between the antennas of the remote station. Depending on the characteristics of the link between a given remote station and its base station. The frequency diversity transmits information on more than one carrier frequency.

The time diversity repeatedly transmits information at time separation that exceeds the coherence time of the channel, so that they will be received in multiple repetitions between the signal with independent fading conditions. There are four categories of methods in diversity reception: 1. Diversity of Selection 2. Diversity of Feedback 3. Combination in Maximum Relationship 4. Diversity of equal gain In the selection diversity, compulsive demodulators are used to provide compulsive diversity branches. The branch of the receiver that has the highest instantaneous SNR is connected to the demodulator. In the Diversity of Feedback, or Exploration, the compulsive m signals are scanned in a fixed sequence until one that is above a predetermined threshold is found. In the Maximum Ratio Combination, the signals of all the branches are weighted according to their voltage ratios of the signal to the individual noise power and then summed. In the equal gain combination, the branch weights are all set to the unit but the signals of each branch are confessed to provide a diversity of compulsives with equal gain ratio. Although frequency diversity is used to mitigate fading, it is not the only means. In a FDD-based system in which the coherence bandwidth can exceed the available bandwidth, the effectiveness of the frequency diversity is not sufficient to prevent fading. The reception on octagonal polarization components are used as complementary means to combat fading. Polarization diversity is used in the PWAN system. . 1 Frequency Diversity The maximum possible frequency separation in an 8 x 2 implementation (spatial x frequency) for the 5 MHZ band is 2.5 MHZ. The frequency separation must exceed a channel coherence bandwidth to minimize the probability that both carriers vanish simultaneously. The coherence bandwidths correspond to correlations of 90% and 50% between the frequencies that are typically used to characterize the channel approximately. An estimate of the coherent bandwidth at a correlation level of 0.90 is given by the equation: 1 B = 50 where is the propagation of the rms delay. When the bandwidth of the coherence is defined for a correlation of 0.50 between the components of the frequency, it becomes 1 B < -t: Table 5.1 lists a correlation level function and the upper and lower limits on the propagation of rms delay measured in PCS bands that includes the observation line and non-linear observation paths. At the 50% correlation level, the upper limit exceeds the 2.5 MHZ frequency separation available for the frequency diversity in a system PWAN FDD. The data presented here is not intended to be the definitive measurement of the expected coherence band events in the deployment of the PWAN. Rather, it is intended to show that given the uncertainty, in the environment, the bandwidth of the coherence can easily exceed the bandwidth of the system available for frequency diversity. Given this, it must be considered another mechanism, such as polarization, for diversity. . 2 Polarization Diversity 5.2.1 Introduction The diversity of polarization exploits the tendency of the multiple path to leak energy from a polarization component transmitted in the octagonal polarization component. For example, a transmitter can transmit a vertically polarized component, but the receiver would receive power in both vertical and horizontal polarization components. If the fading has an effect on one component and not on the other, then the signal could still be received in a different polarization system. . 2.2 Results Polarization diversity for 900 MHZ and 1800 MHZ systems can provide a diversity gain comparable to the horizontal spatial diversity gain. Polarization diversity is used in conjunction with or instead of frequency diversity. Some conclusions are: • The correlation between fading of the horizontal and vertical polarization components in the multiple path that is significantly less than 0.70 for 95% of the time. The correlation values are less than 0.10. • Polarization receiver systems can provide improved operation over a single linear polarization channel in a strong multi-path environment. The operation is comparable with that provided with a horizontal spatial diversity system. • Diversity performance improves when the transmitting antenna strongly excites a horizontal component in addition to the vertical component. This occurs with a 45 degree inclination of linear polarization or circular polarization. In this case, the average signal received experiences a loss of less than ldB compared to a spatial diversity system. * The combination of the maximum ratio of polarization branches is generally assumed on paper. This provides the best performance compared to the selection diversity and equal gain combination. Compared with selection diversity, the combination with the maximum ratio can provide up to 3dB of gain for the benefit of mitigating the effects of the multiple trajectory. • In a multi-path environment, the typical cross-polarization level is approximately -10 dB in relation to the polarization level of the transmitting antenna. . 3 Polarization Diversity System The octagonal polarization components can be de-correlated enough to provide protection against multipath fading.

(However, the high degree of cross-polarization that makes diversity possible works against polarization as an interference suppression mechanism). The implementation scenario for the polarization diversity in the PWAN system is as follows: • Reception of polarization diversity in both the base and the RU. • Transmission with any linear polarization with an inclination of - 45 degrees, or with circular polarization. • Reception with any linear polarization with a dual 45 degree tilt, or with vertical (V) and horizontal (H) components.

• Combination of the polarization branches with the combination of the maximum combination of gain or equal. An exchange between the combination of the maximum optimum ratio and the easy implementation of the equal gain combination will determine the best solution. The resulting invention makes the use of scarce bandwidth resources highly efficient to provide a good service to a large population of users. Although they have been described in the preferred embodiments of the invention in detail above, it will be apparent to those skilled in the art that they can make obvious modifications to the invention without departing from their spirit or essence. Accordingly, as the foregoing description should be taken as illustrative and not restrictive, and the scope of the invention should be determined in view of the following claims. It is noted that in relation to this date, the best method to carry out the aforementioned invention is that which is clear from the present invention.

Claims (41)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A highly efficient bandwidth communications method, characterized in that it comprises the steps of: receiving in the base station a first incoming wireless signal comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of a first remote station during a first time division multiple access (TDMA) interval; receive a second wireless signal at the base station < An entrant comprising a plurality of discrete frequency second tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station during the first time division multiple access (TDMA) interval; receiving at the base station a third incoming wireless signal comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a third remote station during a second multiple access interval by time division (TDMA); receiving at the base station a fourth incoming wireless signal comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a fourth remote station during the second multiple access interval by time division (TDMA); transmitting at the base station the first outgoing wired signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station during the third multiple access interval by division of time (TDMA); transmitting at the base station the second outgoing wireless signal comprising a plurality of quarter discrete frequency tones which are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station during the third interval of multiple access by time division (TDMA); transmitting at the base station the third outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the third remote station during a fourth interval of multiple access by time division (TDMA); and transmitting at the base station the fourth outgoing wireless signal comprising the plurality of quarter discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the fourth remote station during the fourth multiple access interval by time division (TDMA).

2. The highly efficient bandwidth communications method according to claim 1, characterized in that the first and second time division multiple access (TDMA) intervals are part of a TDMA frame interval, the method increases the capacity of communication of the first remote station to the base station, characterized in that it also comprises the step of: receiving in the base station a fifth incoming wireless signal comprising a plurality of first discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM ) in the first frequency band of the first remote station during an additional time division multiple access (TDMA) interval in the TDMA frame interval.

3. The highly efficient bandwidth communications method according to claim 1, characterized in that the third and fourth time division multiple access (TDMA) intervals are part of a TDMA frame interval., the method increases the communication capacity of the base to the first remote station, characterized in that it also comprises the step of: transmitting in the base station a fifth outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by division of orthogonal frequency (OFDM) in the second frequency band to the first remote station during an additional time division multiple access (TDMA) interval.

4. A highly efficient bandwidth communications method, characterized in that it comprises the steps of: receiving in the base station a first incoming wireless signal comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM ) in a first frequency band from a first remote station in a first geographic location during a first time division multiple access (TDMA) interval; receiving in the base station a second incoming wireless signal comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station in a second geographic location during the first time division multiple access interval (TDMA); spatially propagating the first and second incoming signals received at the base station using spatial propagation of weights; receiving at the base station a third incoming wireless signal comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station during the first multiple access interval by time division (TDMA); receiving at the base station a fourth incoming wireless signal comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a fourth remote station during the second multiple access interval by time division (TDMA); grouping spatially first and second outgoing wireless signals at the base station using spatial propagation of weights; transmitting at the base station the first outgoing wireless signal comprising a plurality of discrete frequency third tones which are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station in the first geographical location during the third time division multiple access interval (TDMA); transmitting in the base station the second outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station in the second geographical location during the third time division multiple access interval (TDMA); transmitting at the base station the third outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the third remote station during a fourth interval of multiple access by time division (TDMA); and transmitting at the base station the fourth outgoing wireless signal comprising a plurality of quarter discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the fourth location of the remote station during the fourth interval Multiple time division access (TDMA).

5. The highly efficient bandwidth communications method according to claim 4, characterized in that the spatial propagation step further comprises the steps of: distributing to the base station from a binary source a binary sequence of N data bits in a TDMA interval; convert the binary sequence into a sequence of N-bit symbols; converting the sequence of symbols into a vector having a plurality of P elements; adding the symbol of a Link Control Channel (LCC) to form a vector resulting from a plurality of P + l elements; encode by trellis the resulting vector and produce a vector encoded by a plurality of P + l elements, where each element thereof is a signal within the set of (P + l) QAM signals of the constellation; adding a known pilot symbol to form an output vector of a plurality of P + l elements; weigh the elements of the output vector with the propagation weights according to one of a plurality of antennas Q through which the output vector is to be transmitted; place the elements of the output vector destined for each of the antennas in the inverse DFT frequency trays where they are converted to symbols of the time domain; plot the map of the time domain symbols in discrete frequency output tones; and transmitting the discrete frequency output tones of the base station.

6. The highly efficient bandwidth communications method according to claim 5, characterized in that it further comprises the steps of: repeating the spatial propagation steps for a next binary sequence of N data bits in a successive TDMA interval.

The highly efficient bandwidth communications method according to claim 4, characterized in that the spatial propagation step further comprises the steps of: receiving signals from the base station over the entire plurality of antennas; digitally sample the signals and transform them into a frequency domain; group the transformed signals and add them spatially using the grouping of weights; add the grouped signals of the antennas and form a vector of P + l resulting elements; multiply each element of the vector by a phase correction factor, and separate a pilot symbol from the vector, forming a remaining vector; and encode by trellis the remaining vector to form P traffic data symbols, and 1 LCC data symbol.

The highly efficient bandwidth communications method according to claim 7, characterized in that it further comprises the steps of: repeating the spatial grouping steps in a subsequent TDMA interval.

9. A highly efficient bandwidth communications method, characterized in that it comprises the steps of: receiving in the base station a first incoming wireless signal polarized in a first polarization direction comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of a first remote station during a first time division multiple access (TDMA) interval; receiving in the base station a second incoming wireless signal polarized in a second polarization direction comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station during the first time division multiple access (TDMA) interval; distinguishing the first and second incoming signals received at the base station by detecting the first and second polarization directions; receiving at the base station a third incoming wireless signal comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a third remote station during the first multiple access interval by time division (TDMA); receiving at the base station a fourth incoming wireless signal comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a fourth remote station during the first multiple access interval by time division (TDMA); forming a first and second outgoing wireless signals in the base station by polarizing them in a first and second polarization directions, respectively; transmitting in the base station the first outgoing wireless signal polarized in a first polarization direction comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station in the first geographic location during a third time division multiple access (TDMA) interval; transmitting in the base station the second outgoing wireless signal polarized in the second polarization direction comprising a plurality of discrete frequency third tones which are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station in the second geographical place during the third time division multiple access interval (TDMA); transmitting at the base station a third outgoing wireless signal comprising the plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the third remote station during a fourth interval of multiple access by time division (TDMA); and transmitting at the base station a fourth outgoing wireless signal comprising the plurality of discrete frequency quarter tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the fourth remote station during a fourth multiple access interval by time division (TDMA).

10. The highly efficient bandwidth communications method according to claim 9, wherein the first remote station is in a first geographic location and the second remote station is in a second geographical location, the method is characterized in that it also comprises the steps of: grouping spatially the first and second incoming signals received at the base station using the spatial weights grouping; and spatially propagating the first and second outgoing wireless signals at the base station using the spatial propagation of weights.

11. A highly efficient bandwidth communications method for improving fade resistance, characterized in that it comprises the steps of: receiving in the base station a first incoming wireless signal containing first data, the signal comprising a plurality of first-wavelengths of discrete frequency that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of a first remote station during a first time division multiple access (TDMA) interval, the first signal has a first diversity reception path; receiving at the base station a second incoming wireless signal containing first data, comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the first remote station during the first time division multiple access interval (TDMA), the second signal has a second diversity reception path that is not highly correlated with the first diversity reception path; selecting at the base station the first diversity reception path for the first incoming wireless signal or selecting the second diversity reception path for the second incoming wireless signal to receive the first data; generating in the base station a first outgoing wireless signal to transmit it over a first diversity transmission path and generating a second outgoing wireless signal to transmit over a second diversity transmission path, the first diversity transmission path is not highly correlated with the second path of diversity transmission; transmitting at the base station the first outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station on the first diversity transmission path during a third time division multiple access (TDMA) interval; and transmitting at the base station the second outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the first remote station on the second signal path of diversity during the third time division multiple access interval (TDMA).

12. The highly efficient bandwidth communications method for improving fade resistance according to claim 11, characterized in that it further comprises: the selection step is the maximum ratio combination.

13. The highly efficient bandwidth communications method for improving fade resistance according to claim 11, characterized in that it further comprises: the selection step is the equal gain combination.

14. The highly efficient bandwidth communications method for improving fade resistance according to claim 11, characterized in that it further comprises: the first diversity reception path having a first spatial characteristic and a second reception path of diversity having a second spatial characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path; and the first diversity transmission path having a third spatial characteristic and the second diversity transmission path having a fourth spatial characteristic, so that the second diversity transmission path is not highly correlated with the first path of transmission of diversity. diversity.

15. The highly efficient bandwidth communications method for improving fade resistance according to claim 11, characterized in that it further comprises: the first diversity reception path having a first polarization characteristic and the second reception path of diversity having a second polarization characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path; and the first diversity transmission path having a third polarization characteristic and the second diversity transmission path having a fourth polarization characteristic, so that the second diversity transmission path is not highly correlated with the first path of transmission of diversity.

16. The highly efficient bandwidth communications method for improving fade resistance according to claim 11, characterized in that it further comprises: the first diversity reception path having a first time characteristic and the second diversity reception path which has a second time characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path; and the first diversity transmission path having a third time characteristic and the second diversity transmission path having a fourth time characteristic, so that the second diversity transmission path is not highly correlated with the first path of diversity. transmission of diversity.

17. The highly efficient bandwidth communications method for improving fade resistance according to claim 11, characterized in that it further comprises: the first diversity reception path having a first frequency characteristic and the second reception path of diversity having a second frequency characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path; and the first diversity transmission path having a third frequency characteristic and the second diversity transmission path having a fourth frequency characteristic, so that the second diversity transmission path is not highly correlated with the first path of diversity. transmission of diversity.

18. The highly efficient bandwidth communications method for improving fade resistance according to claim 11, characterized in that it further comprises: the first diversity reception path having a first frequency hopping characteristic and the second path diversity reception having a second frequency hopping characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path; and the first diversity transmission path having a third frequency hopping characteristic and the second diversity transmission path having a fourth frequency hopping characteristic, so that the second diversity transmission path is not highly correlated with the first trajectory of diversity transmission.

19. The highly efficient bandwidth communications method for improving fade resistance according to claim 11, characterized in that it further comprises: receiving in the base station a third incoming wireless signal containing second data, the signal comprises a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station during the first time division multiple access (TDMA) interval, the third signal has a third path of diversity reception; receiving at the base station a fourth incoming wireless signal containing second data, comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the second remote station during the first Time Division Multiple Access Interval (TDMA), the fourth signal has a fourth diversity reception path that is not highly correlated with the third diversity reception path; and selecting at the base station the third diversity reception path for the third incoming wireless signal or selecting the second diversity reception path for the fourth incoming wireless signal to receive the second data;

20. The highly efficient bandwidth communications method for improving fade resistance according to claim 19, characterized in that it further comprises: receiving in the base station a fifth incoming wireless signal comprising a plurality of first discrete frequency tones which are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a third remote station during a second time division multiple access (TDMA) interval; and receiving in the base station a sixth incoming wireless signal comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the fourth remote station during the second multiple access interval by time division (TDMA).

21. The highly efficient bandwidth communications method for improving fade resistance according to claim 20, characterized in that it further comprises: generating in the base station a third outgoing wireless signal for transmitting on a third path of diversity transmission and generating a fourth outgoing wireless signal to transmit on a fourth diversity transmission path, the third diversity transmission path is not highly correlated with the fourth diversity transmission path; transmitting at the base station the third outgoing wireless signal comprising a plurality of quarter discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the second remote station on the third diversity transmission path during the third time division multiple access (TDMA) interval; and transmitting at the base station the fourth outgoing wireless signal comprising a plurality of quarter discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the second remote station on the fourth signal path of diversity during the third time division multiple access interval (TDMA).

22. The highly efficient bandwidth communications method for improving fade resistance according to claim 21, characterized in that it further comprises: transmitting at the base station a fifth outgoing wireless signal comprising the plurality of discrete frequency third tones which are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the third remote station during a fourth time division multiple access (TDMA) inter and transmitting at the base station a sixth outgoing wireless signal comprising the plurality of quarter discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the fourth remote station during the fourth multiple access interby time division (TDMA).

23. A highly efficient bandwidth communications method for improving fade resistance, characterized in that it comprises the steps of: receiving in the base station a first incoming wireless signal containing first data, the signal comprises a plurality of first-wavelengths of discrete frequency that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of a first remote station during a first time division multiple access (TDMA) inter the first signal has a first diversity reception path; receiving at the base station a second incoming wireless signal containing first data, comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the first remote station during the first time division multiple access inter(TDMA), the second signal has a second diversity reception path that is not highly correlated with the first diversity reception path; selecting at the base station the first diversity reception path for the first incoming wireless signal or selecting the second diversity reception path for the second incoming wireless signal to receive the first data; generating in the base station a first outgoing wireless signal and generating a second outgoing wireless signal; transmitting at the base station the first outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the first remote station during a third interof multiple access by time division (TDMA); and transmitting at the base station the second outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the first remote station during the third multiple access interby time division (TDMA).

24. The highly efficient bandwidth communications method for improving fade resistance according to claim 23, characterized in that it further comprises: the selection step is the maximum ratio combination.

25. The highly efficient bandwidth communications method for improving fade resistance according to claim 23, characterized in that it further comprises: the selection step is the equal gain combination.

26. The highly efficient bandwidth communications method for improving fade resistance according to claim 23, characterized in that it further comprises: the first diversity reception path having a first spatial characteristic and a second reception path of diversity that has a second spatial feature, so that the second diversity reception path is not highly correlated with the first diversity reception path.

27. The highly efficient bandwidth communications method for improving fade resistance according to claim 23, characterized in that it further comprises: the first diversity reception path having a first polarization characteristic and the second reception path of diversity having a second polarization characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

28. The highly efficient bandwidth communications method for improving fade resistance according to claim 23, characterized in that it further comprises: the first diversity reception path having a first time characteristic and the second reception path of diversity having a second time characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

29. The highly efficient bandwidth communications method for improving fade resistance according to claim 23, characterized in that it further comprises: the first diversity reception path having a first frequency characteristic and the second reception path of diversity having a second frequency characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

30. The highly efficient bandwidth communications method for improving fade resistance according to claim 23, characterized in that it further comprises: the first diversity reception path having a first frequency hopping characteristic and the second path diversity reception having a second frequency hopping characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

31. A highly efficient bandwidth communications method for improving fade resistance according to claim 23, characterized in that it further comprises: receiving in the base station a third incoming wireless signal containing second data, the signal comprising a plurality of seconds discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of a second remote station during a first time division multiple access (TDMA) interval, the third signal has a third reception path of diversity; receiving at the base station a fourth incoming wireless signal containing second data, comprising a plurality of second discrete frequency tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the second remote station during the first Time Division Multiple Access Interval (TDMA), the fourth signal has a fourth diversity reception path that is not highly correlated with the third diversity reception path; and selecting at the base station the third diversity reception path for the third incoming wireless signal or selecting the fourth diversity reception path for the fourth incoming wireless signal to receive the second data.

32. A highly efficient bandwidth communications method for improving fade resistance, characterized in that it comprises the steps of: receiving a first incoming wireless signal containing a first data at a remote station, the signal comprises a plurality of first-wave tones, discrete frequency that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of a base station during a first time division multiple access (TDMA) interval, the first signal has a first diversity reception path; receiving at the remote station a second incoming wireless signal containing first data, comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the base station during the first interval TDMA), the second signal has a second diversity reception path that is not highly correlated with the first diversity reception path; selecting at the remote station the first diversity reception path for the first incoming wireless signal or selecting the second diversity reception path for the second incoming wireless signal to receive the first data; generating in the remote station a first outgoing wireless signal and generating a second outgoing wireless signal; transmitting at the remote station the first outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in a second frequency band to the base station during a third division multiple access interval of time (TDMA); and transmitting at the remote station the second outgoing wireless signal comprising a plurality of discrete frequency third tones that are multiplexed by orthogonal frequency division (OFDM) in the second frequency band to the base station during the third multiple access interval by time division (TDMA).

33. The highly efficient bandwidth communications method for improving fade resistance according to claim 32, characterized in that it further comprises: the selection step is the maximum ratio combination.

34. The highly efficient bandwidth communications method for improving fade resistance according to claim 32, characterized in that it further comprises: the selection step is the equal gain combination.

35. The highly efficient bandwidth communications method for improving fade resistance according to claim 32, characterized in that it further comprises: the first diversity reception path having a first spatial characteristic and a second reception path of diversity having a second spatial characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

36. The highly efficient bandwidth communications method for improving fade resistance according to claim 32, characterized in that it further comprises: the first diversity reception path having a first polarization characteristic and the second reception path of diversity having a second polarization characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

37. The highly efficient bandwidth communications method for improving fade resistance according to claim 32, characterized in that it further comprises: the first diversity reception path having a first time characteristic and the second reception path of diversity having a second time characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

38. The highly efficient bandwidth communications method for improving fade resistance according to claim 32, characterized in that it further comprises: the first diversity reception path having a first frequency characteristic and the second reception path of diversity having a second frequency characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

39. The highly efficient bandwidth communications method for improving fade resistance according to claim 32, characterized in that it further comprises: the first diversity reception path having a first frequency hopping characteristic and the second reception path of diversity having a second frequency hopping characteristic, so that the second diversity reception path is not highly correlated with the first diversity reception path.

40. The highly efficient bandwidth communications method for improving fade resistance according to claim 32, characterized in that the first time division multiple access (TDMA) interval is part of a range of the TDMA frame, the The method increases the communication capability of the base station to the remote station, characterized in that it also comprises the step of: receiving in the remote station an additional incoming wireless signal comprising a plurality of discrete frequency first tones that are multiplexed by frequency division Orthogonal (OFDM) in the first frequency band of the first base station during an additional time division multiple access (TDMA) interval in the TDMA frame interval.

41. A highly efficient bandwidth communications method for improving fade resistance, characterized in that it comprises the steps of: receiving in a base station a first incoming wireless signal containing first data, the signal comprising a plurality of first-order tones, discrete frequency that are multiplexed by orthogonal frequency division (OFDM) in a first frequency band of a first remote station during a first time division multiple access (TDMA) interval, the first signal has a first diversity reception path , the first time division multiple access (TDMA) interval is part of a TDMA frame interval; receiving at the base station a second incoming wireless signal containing first data, comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the first remote station during the first time division multiple access interval (TDMA), the second signal has a second diversity reception path that is not highly correlated with the first diversity reception path; selecting at the base station the first diversity reception path for the first incoming wireless signal or selecting the second diversity reception path for the second incoming wireless signal to receive the first data; and increasing the communication capability of the remote station to the base station selectively, receiving in the base station an additional incoming wireless signal comprising a plurality of discrete frequency first tones that are multiplexed by orthogonal frequency division (OFDM) in the first frequency band of the first remote station during an additional time division multiple access (TDMA) interval in the TDMA frame interval.