HK1069059A - System and method for frequency re-use in a sectorized cell pattern in a wireless communication system - Google Patents

Description

System and method for frequency reuse in sectorized cell mode in wireless communication system

RELATED APPLICATIONS

The present application relates to: co-pending, commonly assigned U.S. patent application serial No. 09/434,707 entitled "system and method for wideband millimeter wave data communication," co-pending, commonly assigned U.S. patent application serial No. 09/604,437 entitled "maximizing efficiency using a dynamically asymmetric multicarrier time division multiplexing system," and co-pending, commonly assigned U.S. patent application serial No. 09/607,456 entitled "frequency reuse for TDD," which are incorporated herein by reference. This patent application is also filed concurrently with a commonly assigned U.S. patent application entitled "system and method for in-band signaling for sector synchronization in a wireless communication system".

Technical Field

The present invention relates to communication systems and methods, and more particularly, to a system and method for optimizing bandwidth in a point-to-multipoint wireless system by synchronizing transmit and receive modes.

Background

Wireless links have become increasingly important in providing data communication links for various applications. For example, internet service providers have begun to use wireless links in urban environments to avoid the installation costs of traditional wired connections or optical fibers. It is better to use a wireless link system in a point-to-multipoint architecture to provide services to multiple users. A point-to-multipoint system is typically made up of multiple hub devices that serve multiple child devices (sometimes referred to as remote devices, nodes, or user devices). These sub-devices are typically associated with a single node on the system. For example, a single kid device may be connected to a LAN to allow a PC on the LAN to bridge to other networks through such a point-to-multipoint system. Each sub-device communicates with a particular hub device over a wireless channel. In a point-to-multipoint system, a hub device may control communications between a portion of a plurality of sub-devices associated with a particular coverage area. The hub device schedules transmit and receive bursts to and from the kid device. The hub device may distribute data packets received from a particular sub-device to another sub-device, a conventional wired network backbone, or another hub device within the same coverage area via the frames.

A point-to-multipoint system, such as that disclosed in the above-referenced and commonly assigned patent application entitled "frequency reuse for TDD," includes a plurality of adjacently disposed hub devices providing a collective coverage area. In addition, these hubs may have their respective coverage areas divided into specific sectors, such as 30 or 90 degree sectors. Additionally, these hubs may provide multiple communication channels using frequency division or other techniques.

Channel reuse techniques have been developed to allow reuse of channels within a network without introducing unacceptable levels of interference. The purpose of these channel reuse techniques is to maximize channel availability while avoiding co-channel interference between adjacent hubs. Clearly, these channel reuse techniques are important tools for increasing the bandwidth of point-to-multipoint systems. However, in accordance with the present invention, it has been recognized that the architectural features incorporated in a point-to-multipoint system can be used to optimize channel availability over that available using conventional channel reuse techniques while avoiding co-channel interference.

For example, data traffic through a point-to-multipoint system may be bursty, rather than at a fixed or continuous data rate. In particular, an internet browser application executing on a sub-device typically requires a large amount of downlink bandwidth when downloading HTML code from a site, and little or no bandwidth is required for a user to read a display associated with the HTML code. In addition, the bandwidth requirements of many applications, such as browsers, may be asymmetric. In particular, internet browsers often download large amounts of data, but the amount of upload is very small in proportion. Thus, point-to-multipoint systems may implement Dynamic Bandwidth Allocation (DBA) techniques to maximize data throughput associated with asymmetric, bursty traffic.

Disclosure of Invention

It is therefore an object of the present invention to provide a system and method that maximizes the bandwidth of a point-to-multipoint system based on the unique characteristics of the point-to-multipoint system between particular portions of the network.

It is another object of the present invention to provide a system and method for synchronous dynamic allocation of bandwidth.

It is another object of the present invention to provide a system and method for synchronizing the reception and transmission patterns of the sectors or other portions of the associated group of hub devices to maximize the bandwidth of a point-to-multipoint system.

It is another object of the present invention to provide a system and method for sector-to-sector telemetry in a point-to-multipoint system.

It is another object of the present invention to provide an efficient communication channel for use with the system and method of the present invention that allows for synchronization of adjacent hubs while a single hub dynamically allocates bandwidth quickly.

It is another object of the present invention to provide a frequency reuse mode in a wireless communication system.

It is another object of the present invention to provide a repeatable frequency reuse pattern in a wireless communication system consisting of 16 cells in a 4 x 4 grid using two polarizations per communication frequency.

It is another object of the present invention to provide a repeatable frequency reuse pattern in a wireless communication system consisting of 16 cells combined into 4 sub-clusters of 4 cells, wherein opposite sectors in the pattern are synchronized.

It is a further object of this invention to provide a method of reducing co-channel and/or adjacent channel interference through frequency reuse patterns.

These and other objects, features and technical advantages of the present invention are achieved by a system and method for operating a point-to-multipoint system comprising a plurality of hubs and a plurality of sub-devices distributed within a coverage area associated with the hubs. Point-to-multipoint systems preferably utilize spectral division techniques, such as frequency division, time division, or orthogonal code division, to divide their communication bandwidth into channels. And the hubs communicate with the sub-devices within their coverage areas through sector antennas. By utilizing spectral partitioning and sector antennas, the preferred embodiment of the point-to-multipoint system coordinates channel allocation through a channel reuse scheme. In addition, the preferred embodiment divides a single channel into transmission and reception modes through a Time Division Duplex (TDD) scheme via the same channel. In this TDD scheme, the hub transmits information to the kid device in the transmit mode and receives information from the kid device in the receive mode. In addition, the hub of the point-to-multipoint system preferably dynamically allocates bandwidth between transmit and receive modes to implement an asymmetric communication mode. The sub-device utilizing the preferred embodiment of the present invention also includes a directional antenna.

Co-channel interference, such as in adjacent sectors of adjacent hubs, is a serious problem, particularly hub-to-hub exposure, since hub antennas are typically directed at other hubs of the network to provide composite coverage for the service area. For example, the hub of the preferred embodiment may utilize sector antennas covering orientations between 30 and 90 degrees, with these antennas oriented to face similar sector antennas located at adjacent hubs. The sub-equipment exposure is not a serious problem for the point-to-multipoint systems of the preferred embodiment because the sub-equipment of these point-to-multipoint systems use highly directional antennas. Thus, the kid device does not experience severe co-channel interference from other kid devices or other hub devices.

Channel reuse schemes may be used to reduce hub-to-hub co-channel interference. For example, by carefully allocating the channels used by the hubs of the network, reuse performance approaching 1 can be achieved. Further, higher channel reuse performance may be achieved through advanced channel planning techniques, as illustrated and described in the above-referenced patent application entitled "TDD frequency reuse," and as will be described below.

However, methods or system optimizations that allow for higher channel reuse rates will increase the overall bandwidth of the system. The present invention accomplishes this in one embodiment by synchronizing the transmit and receive modes of the hub. One embodiment of the present invention synchronizes dynamic bandwidth allocation to face sectors in a cluster of geographically adjacent hubs, while allowing other sectors of these hubs to independently allocate bandwidth through frequency reuse and face sector synchronization. Hub adjacency means that these hubs are nearest neighbors in a particular direction. In this embodiment, the guard time between transmit and receive modes is minimized by optimizing the guard time to accommodate the synchronization distance that happens to span the two hub coverage radii. For example, when the maximum reuse is 6R, the reuse schedule is 9, a 30 degree sector is employed, and a 4.5 km cell, the guard time is close to 100 microseconds, or close to 5% of the channel capacity of the present embodiment, to provide propagation from the maximum distance in the reuse cluster. However, because the present invention synchronizes the opposite sectors of adjacent hubs, the synchronization distance is greatly shortened. Thus, in this embodiment, the guard time occupies only.5% of the channel capacity. Furthermore, the computational requirements of the system are greatly reduced in this preferred embodiment because fewer parts of the network are synchronized for any particular synchronization determination. And synchronizing the face sectors simplifies implementation of synchronous telemetry.

In another embodiment of the present invention, a frequency reuse pattern is described in which a repeatable cell pattern is utilized to allow reuse of multiple frequency assignments in which two polarization patterns per frequency are available. Such a frequency reuse pattern is particularly useful when the number of frequency assignments or communication channels available to operate the communication system is limited. In order to provide adequate coverage for a particular operating region, a cell pattern that reuses these available frequencies must be provided to avoid blind spots, or to avoid interference between adjacent channels on the spectrum used by the same region (such interference is referred to in the art as "adjacent channel interference"), or to avoid interference between two cells of the same polarization and same frequency in adjacent regions (such interference is referred to in the art as "co-channel interference").

By idealising the cell shape in this pattern to be circular and further idealising each cell to have a similar radius, the shape of the repeatable pattern of such cells can be considered to be coverage on a plane. Obviously, such idealization, as planes and substantially identical cells spaced by consistent distances, is rare in the real world. It should be understood, however, that the system and method of the present invention is not limited to such idealization, but is applicable to real-world environments in which all frequency reuse patterns may be used, taking into account minor variations to account for blockage, terrain features, different cell sizes, irregular cell spacing, etc. Although the following description of the invention will discuss idealized repeatable patterns consisting of idealized cells and the like, such idealization should not be considered as limiting the invention.

For cells of substantially the same size and circular shape, one arrangement of these cells in a multi-cell pattern can be seen as a square grid, where the edges of two adjacent cells in the same row or column are tangent at a point. In this arrangement, the diagonally adjacent cells are not tangent. In another multi-cell arrangement, the cells in the pattern are all tangent to 6 neighboring cells. If the cells are idealized as hexagons, this pattern will appear as a honeycomb shape.

The inventors have empirically determined that for a cell with a 90 sector, a minimum of 8 frequency assignments and two polarizations are required for efficient frequency reuse for a broadband wireless access system. This is a reasonable requirement for frequency/polarization assignment for 90 sectorized cells in time division duplex ("TDD") systems based on consideration of typical license allocation sizes for global range frequencies. For example, in Europe, the license allocation expected for the 28GHz band is 2X 112MHz or 224MHz, while for the 42GHz band it is close to 500 MHz. Most north american broadband wireless access operators have frequency allocations in excess of 200 MHz. The prevailing channel size emerging in europe is 28MHz and in north america is 25 MHz. These channel sizes plus the expected license allocation of frequencies leave room for 8 or more available frequency channels.

While 90 sectors have some inconveniences compared to smaller sector sizes, such as 60, 45, and 30 sectors, 90 sector sizes are a planning benchmark for almost all broadband wireless access operators and standards organizations. For example, wide sector versus narrow sector RF performance is somewhat compromised. The cell diameter is reduced so that a greater number of hubs/cells are required to cover a given area. Wider sectors will also cause a greater likelihood of co-channel and adjacent channel interference.

Although the 90 sector has operational drawbacks, the 90 sector scheme has important economic advantages. One advantage is the lower cost of the outdoor equipment. Because of the 90 ° sector, fewer sectors are required compared to a smaller size sector, thereby requiring fewer radios, antennas, and associated equipment, whether primary or redundant. In addition, one significant overhead for operators is the rooftop rights, and property owners tend to charge the right to place equipment on the rooftop of their buildings based on the number of antennas, so a 90 sector means that the overhead for the rooftop rights is lower. Moreover, wider sectors can provide greater RF coverage, which is of great significance in early deployment of the system.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.

Drawings

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 depicts an example of a point-to-multipoint system arranged in a cluster architecture;

FIG. 2A depicts a schematic sector configuration of the point-to-multipoint system shown in FIG. 1;

FIG. 2B illustrates a sectorized antenna arrangement of the hub for one of the cells in FIG. 2A;

FIG. 3 illustrates a particular sector and the propagation of transmissions from a hub to a plurality of sub-devices within the particular sector;

FIGS. 4A-4D each illustrate timing diagrams of a series of RX and TX frames associated with the sector reversal of a neighboring hub;

fig. 5 illustrates an exemplary power diversity spectrum of a QAM carrier signal and an associated adaptive carrier;

fig. 6A illustrates a set of 8 frequency channels each having two polarizations for frequency incumbent;

FIG. 6B illustrates 8 unique cell types utilizing a set of 8 frequency channels with two polarizations per frequency channel as shown in FIG. 6A;

figure 7 illustrates a repeatable pattern of 16 cells in a 4 x 4 rectilinear grid, each cell divided into 4 90 sectors, with opposing sectors operating on the same frequency channel with the same polarization;

fig. 8 illustrates a 4-cell combination of the 16-cell repeatable pattern from fig. 7;

fig. 9 illustrates a 16-cell repeating pattern in a 4 x 4 grid forming a parallelogram, wherein each cell is divided into 4 90 ° sectors, the opposite sectors operating on the same frequency channel with the same polarization;

FIG. 10 illustrates the repeatable pattern of FIG. 7, wherein the opposite sector operates on the same frequency channel and polarization-allowing synchronization of transmission and reception between the hub antennas of the opposite sector;

FIG. 11A illustrates a set of 8 frequency channels having two polarizations per frequency channel as shown in FIG. 6A, indicating the frequency channels and polarizations used in the mode of FIG. 10 and the frequency channels and polarizations not used in the retained mode of FIG. 10;

FIG. 11B illustrates 8 unique cell types using a set of 4 frequency channels with two polarizations per frequency channel as shown in FIG. 11A for the frequency reuse pattern of FIG. 10;

fig. 12 illustrates a 4-cell combination from the 16-cell repetition pattern of fig. 10;

FIG. 13 illustrates a repeatable pattern with additional frequency channel sector overlap to increase the capacity requirements of system users;

Detailed Description

Fig. 1 illustrates an exemplary point-to-multipoint system to which the present invention is applied. The system is preferably deployed in a cluster configuration. The illustrated cluster is made up of a plurality of hubs (105, 106, 107, 108), although a different number of clusters than the illustrated configuration may be used in accordance with the invention. It should be understood that a communication network to which the present invention is applied may also comprise further clusters, either remotely or adjacently located to the cluster to which the present invention is applied.

Hubs 105, 106, 107 and 108 provide coverage for cells 101, 102, 103 and 104. A plurality of sub-devices (109) and 119 are deployed in the cells 101, 102, 103 and 104, respectively. In addition, a processor system (120-131) is respectively associated with each sub-device. It should be understood that the sub-devices of the point-to-multipoint system may also be associated with the LAN network of the processor system. Alternatively, the sub-devices of the point-to-multipoint system may be connected to an intermediate network. For example, the kid device may be connected to an intermediate ATM switch. It should also be understood that a system applying the present invention may contain any of a large number of hubs, cells, and sub-devices. To simplify the description of the present invention, the exemplary embodiment is described by taking 4 cells as an example.

Fig. 2A illustrates an exemplary sector configuration of the point-to-multipoint system shown in fig. 1. As previously noted, the system is divided into coverage areas associated with cells 101, 102, 103, and 104. Further, the cells 101, 102, 103, and 104 of the present example are sectorized into 90 sectors (101A-101D, 102A-102D, 103A-103D, and 104A-104D), although other sector sizes may be synchronized in accordance with the present invention. Hubs 105, 106, 107, and 108 transmit and receive signals to and from sectors via sector antennas, as illustrated for hub 105 in fig. 2B. Sector antennas 202A-202D may utilize a separate antenna element for each sector. Alternatively, a sector antenna may utilize multiple narrow beam antenna elements to synthesize sector coverage. In this configuration, the radio frequency signal energy transmitted from the sector antennas associated with any of sectors 101D, 102C, 103B, and 104A can be detected in the other sector antennas of this combination.

The spectrum allocated to the point-to-multipoint system is preferably subdivided into channels in general. The present invention can use various channel division methods such as time division, frequency division channel, frequency hopping channel, and orthogonal code channel. The channels are divided into discrete sets. In addition, a set of channels is allocated among the sectors of the point-to-multipoint system according to a reuse procedure. In this exemplary system, to illustrate the present invention, the RF signal 302 and 307 are transmitted over the same channel. It should be understood that other signaling may also occur on other channels concurrently with the example transmit and receive signals.

According to a preferred embodiment, at least adjacent sectors of a particular cell are provided in different channel sets according to a channel reuse scheme. For example, the assigned channels used for sectors 104B and 104C are different than the assigned channels used for sector 104A. However, depending on the front-to-back separation of sector antennas, sidelobe performance, etc., the channel set may also be reused in a cell, such as within sectors 104B and 104C and/or 104A and 104D.

Fig. 3 illustrates a series of RF transmit signals (301-306) broadcast from hubs 105 and 106, respectively. Hub 105 transmits a series of RF time bursts or time slot signals (302, 303, and 304) traveling in direction 301 within sector 101D. Because hub 105 uses sector antennas, energy associated with RF signals 302, 303, and 304 propagates through sector 101D. The RF signal 302 contains information of the sub-device 109. The RF signal 303 contains information of the kid device 110. The RF signal 304 contains information of the kid device 111. Similarly, hub 108 transmits a series of RF time-collision or time-slot signals (305, 306, and 307) traveling in direction 308 within sector 104A. Because hub 104 uses sector antennas, energy associated with RF signals 305, 306, and 307 propagates through sector 104A. The RF signal 305 may contain information of the kid device 117. The RF signal 306 may contain information for the kid device 118. The RF signal 307 may contain information of the kid device 119.

Eventually, RF signals 302, 303, and 304 will propagate beyond the bounds of cell 104 to reach cells 101, 102, and 103. Thus, RF signals 302, 303, and 304 may cause co-channel interference in cells 101, 102, and 103. In the point-to-multipoint system of the preferred embodiment, the kid device utilizes highly directional antennas directed toward the associated hub, and thus, is generally remote from the remaining hubs of a cluster. Thus, the kid device is generally not subject to co-channel interference from the RF signals 302, 303, and 304.

However, when the RF signal arrives at a particular hub, if the hub is in receive mode for a particular channel associated with RF signals 302, 303, and 304, hubs 105, 106, and 107 will experience co-channel interference. According to a preferred embodiment, hub 108 uses the same set of channels for sector 104A as hub 105 for sector 101D, hub 106 for sector 102C, and hub 107 for sector 103B. Thus, RF signals 302, 303, and 304 may cause co-channel interference depending on the time they arrive at hubs 106, 107, and 108. It should be appreciated that if RF signals 302, 303, and 304 arrive while hubs 106, 107, and 108 are in transmit mode, the effect of RF signals 302, 303, and 304 is negligible. Similarly, if the hub is in receive mode for the channels associated with RF signals 305, 306, and 307 as they arrive, RF signals 305, 306, and 307 may cause co-channel interference at hubs 105, 106, and 107.

In addition, the sub-devices in sectors 101D and 104A broadcast RF signals 309 and 314. It was previously noted that the subset of the preferred embodiment of this system uses highly directional antennas. The structure of such a system is such that the highly directional antenna concentrates the radiated RF energy into a very narrow beam centered on the corresponding hub. Therefore, the probability that these sub-devices will couple to another antenna in the system and cause co-channel interference is small. It should be understood that this exemplary system assumes that RF signals 302 and 207 and 309 and 314 are transmitted over the same channel. Thus, this exemplary system illustrating the present invention controls the timing of the transmission of the RF signals during the TDMA burst period.

The preferred embodiment of the present invention and method synchronizes specific transmissions within a point-to-multipoint system to prevent the hub transmissions from causing co-channel interference. Of course, in addition to transmit window synchronization, the receive windows may also be synchronized in accordance with the present invention. Depending on the amount of separation between channels, it may be possible to independently synchronize individual channels within adjacent sectors. By synchronizing the individual channels, the adaptive time division duplex scheme can maximize throughput on a per channel basis. However, this scheme requires a large amount of processing power and therefore higher equipment cost and complexity to calculate the optimum receive and transmit asymmetry. Thus, the preferred embodiment enables simultaneous transmission and reception of all channels used in adjacent sectors. In this manner, the system and method of the present invention enables higher performance asymmetric time division duplex algorithms while maintaining a preferred level of cost and complexity.

Fig. 4A-4D depict example timing diagrams of transmit and receive frames for sectors 101D, 102C, 103B, and 104A of hubs 105, 106, 107, and 108. Each hub is preferably synchronized to begin its transmit mode at time t 0. Hub 105 transmits TX bursts 401-403 that respectively contain information for sub-devices 109-111. Hub 106 transmits TX burst 404 containing information for kid device 114. Hub 107 transmits bursts 405 and 406 that contain information for kid devices 115 and 116, respectively. Hub 108 transmits bursts 407 and 409, which respectively contain information for sub-devices 117 and 119. Furthermore, it is preferable to synchronize each hub so that at time t₆Ending its transmission mode.

In addition, the hubs 105 and 108 are synchronized so that the hubs 105 and 108 are synchronized from the time t₆To time t₇And does not emit. Furthermore, the hubs 105 and 108 are started from time t₆To time t₇No burst is received from the kid device. During this period, the transmit and receive delays create a guard time 316. The duration of the guard time 316 is preferably such that the RF signal associated with the corresponding burst propagates out of any hub that may experience co-channel interference before the hub will enter a receive mode. The adjacent sectors are synchronized such that the synchronization distance in this embodiment is slightly greater than the two hub radii (the distance between hubs 105 and 108). Adjacent fan with proper reuse planZone synchronization is already sufficient because the non-synchronized sector space separation using these channels will be large enough or facing different directions to avoid co-channel interference.

An exemplary discussion of such frequency reuse plans is contained in the above-referenced patent application entitled "TTD frequency reuse". In an environment using frequency reuse, hubs and their respective sectors may be assigned channels by storing the assigned channels in non-volatile memory of the hub for physically configuring the hubs during a configuration boot operation. Alternatively, channels may be dynamically assigned according to a dynamic channel assignment algorithm. In this case, the channel controller may implement a specific dynamic assignment algorithm and periodically communicate the assigned channels to the hub for the respective sectors.

At time t₇The hubs 105 and 108 synchronize to enter a receive mode. At this point, the hubs 105 and 108 may receive transmissions from their respective sub-devices without detecting RF signals transmitted from other hubs. During receive mode, hub 105 receives RX bursts 410 and 412 from sub-devices 109 and 111, respectively. Hub 106 receives RX burst 413 from child device 114. Similarly, hub 107 receives RX bursts 414 and 415 from child devices 115 and 116, respectively. Hub 108 receives RX bursts 416 and 418 from sub-devices 117 and 119, respectively. The hubs 105 and 108 are preferably synchronized to be at time t₁₃Ending their receive mode.

In addition, this embodiment has other advantages. First, adjacent hubs are able to communicate directly, and thus frame timing and/or channel allocation can be coordinated without the need for a separate telemetry line. Second, the telemetry bandwidth necessary to coordinate channel allocation in a synchronous manner is greatly reduced in adjacent hub configurations. Furthermore, the computational capacity required for adjacent sector synchronization is much less than cluster-wide synchronization.

It should be appreciated that the present invention enables higher system utilization and performance through considerations other than higher channel reuse. By synchronizing adjacent sectors or adjacent antenna beams, the present invention does not impose any other arbitrary restrictions on the transmit and receive asymmetry associated with other sectors or antenna beams. For example, it is possible that the sub-devices in adjacent sectors require a large amount of transmit bandwidth in total, but only a very small receive bandwidth at a particular time. While it is possible that the sub-devices of non-adjacent sectors will require the opposite bandwidth requirements altogether. If the entire group of sectors is synchronized, a portion of the bandwidth will be wasted in both adjacent and non-adjacent sectors. Thus, the present invention operates adjacent sector transmit and receive asymmetry independently of other asymmetries. By separating the asymmetric relationships, the system can accommodate the bandwidth requirements inherent in the overall system that change at each time.

It should also be understood that the present invention does not require that the hubs 105 and 108 begin or end their transmit or receive modes at exact moments in time. However, more precise synchronization will shorten the guard time, thereby maximizing the throughput of the system. Furthermore, the present invention does not require any particular channel bandwidth allocation for the sub-devices. It should be understood that any number of channel division techniques may be used. All bandwidth may be allocated to a particular sub-device during a single transmit/receive period. Alternatively, in a TDM/TDMA scheme, each sub-device in a sector may receive a designated portion of the available bandwidth every transmit/receive cycle. Alternatively, the sub-device bandwidth may be allocated according to a polling scheme. The hub may implement any number of algorithms to schedule bandwidth for a particular sub-device. The receive and transmit modes may also be divided by other techniques. For example, the sub-device may send bursts to the hub using CSMA/CD techniques. Alternatively, the system may utilize contention periods and contention-free periods for the sub-devices to access the communication channel.

It should be understood that various other signaling may occur between the hub and the kid device on the selected channel in accordance with the present invention. For example, the hub may transmit a broadcast burst intended for all the kid devices. The hub may transmit a control channel burst. In addition, the hub may send a beacon signal containing timing information or a network allocation vector to synchronize the kid device with the hub. These signaling may include requesting a transmission, allowing a transmission, or acknowledging a data burst.

It should be understood that the present invention does not require strict definition of the transmission and reception modes. For example, TDM/TDMA telephony systems strictly define the timing and duration of receive and transmit patterns to optimize the system for transmitting voice traffic. Instead, the present invention can work within a system with asymmetric transmit and receive modes. Furthermore, the invention can also be used in systems where the duration of the transmit and receive modes is dynamically changed. Exemplary dynamic bandwidth allocation systems and methods usable with the present invention are described in the above-referenced patent application entitled "systems and methods for wideband millimeter-wave data communication". In accordance with a preferred embodiment, to facilitate dynamic changes in the bandwidth allocated to transmit and receive modes, the hub of the preferred embodiment has a synchronization sector that communicates these changes to the corresponding hub and/or common control system. Thus, another aspect of the present invention can provide a telemetry communication channel for synchronizing transmit and receive modes of a co-channel coupled hub.

Several schemes may be employed to provide such a communication channel. A leased connection from ILEC (overlay. However, it is preferred to use communication resources associated with point-to-multipoint systems instead of ILEC connections. Thus, sector synchronization telemetry may use the backhaul associated with a point-to-multipoint network. The backhaul may be implemented in any form of communication device, such as a broadband fiber optic gateway or other broadband data-level connection, a T1 communication line, a wired communication system, and so forth. However, other systems connected to the backhaul or to the backhaul are required for each hub of the cluster to achieve sector synchronization with such control channels. While this may be sufficient in many systems, it is not an optimal solution as a particular system may have a hub that is not connected to the backhaul.

Fig. 5 illustrates a preferred option involving synchronized telemetry of a narrow carrier band adjacent to a main carrier band. In a preferred embodiment of the invention, the spectrum of the point-to-multipoint system is divided into discrete 50MHz channels. The basic data communication is realized by a Quadrature Amplitude Modulation (QAM) carrier 501 occupying about 46 MHz. In addition, narrowband self-establishment is carried out in the protection space of 50MHz channelA carrier wave 502 is adapted, preferably with a bandwidth of 130kHz, to provide synchronous telemetry. The hub preferably utilizes two-pole FSK modulation to communicate information over an adaptive carrier 502. In a preferred embodiment, the adaptive carrier 502 contains a 100Kbps signaling rate for 10^-1210dB C/N for BER, 1/2 concatenated coding, and a transmit power 10dB below QAM power level. By utilizing this type of channel, control channels may be transmitted and/or received through adjacent sector antenna beams of a particular cluster of hubs.

It should be appreciated that the narrowband adaptive carrier 502 provides a preferred signaling channel optimized for a 50MHz system. However, it should be understood that the telemetry control channel need not be implemented as a narrowband carrier. If the present invention is used in a wideband point-to-multipoint system, the telemetry control channel may be spread spectrum processed across a larger spectrum. In addition, it is not necessary to place the adaptive carrier 502 in the guard space associated with the predetermined channel. Adaptive carriers may be implemented with explicitly allocated spectrum.

In a preferred embodiment, neighboring hubs utilizing the present invention can receive bandwidth requests from their respective sub-devices. The hub may perform calculations based on bandwidth calculations. In this type of system, the bandwidth controller may be located at a hub to receive the results of the bandwidth calculations over the adaptive carrier 502. Alternatively, the bandwidth controllers may be implemented as independent system links to the respective hubs.

The bandwidth controller uses the received calculations to determine the optimum transmit and receive pattern durations for the synchronized sectors. The control hub communicates the determined transmit and receive mode durations to the hub using an adaptive carrier. The hubs use these durations at this time to allocate transmit and receive resources for their respective sub-devices in adjacent sectors. It should be understood that the controller may receive the bandwidth request and perform the calculation directly. However, it is preferable to perform the computation at the hub because it more efficiently distributes the processing requirements. It should also be understood that the hub may contain logic to control the receive and transmit modes in the event that the adaptive carrier link is interrupted. For example, the hub may temporarily revert to a predetermined length for transmit and receive mode. Alternatively, the hub may temporarily define transmit and receive modes of equal length.

For example, the bandwidth controller of the present invention can monitor instantaneous traffic demand on the forward and reverse links to determine the proper amount of ATDD and/or asymmetry with which to operate the carrier channel. The bandwidth controller of the preferred embodiment of the present invention may operate on the processor (CPU) and associated memory (RAM) of the hub of the present invention. The controller may include a record of adjacent antenna beams and corresponding channels in a non-volatile register to achieve the desired synchronization. Alternatively, the bandwidth controller may operate in an environment where sectors are dynamically changed and/or channels are dynamically allocated to various sectors. In this environment, the bandwidth controller may communicate with the portion of the system that affects the sector configuration and/or channel allocation algorithm to obtain information relating to neighboring antenna beams and their channels. Of course, additional and/or other devices, such as a general purpose computer system-based processor with appropriate algorithms to control its operation, may be used to operate the bandwidth controller of the present invention.

Referring now to fig. 6A, a set 600 is a conceptual depiction of 8 available channels, also referred to herein as "frequencies," of a communication system available for two polarizations per channel. The set of frequencies 601 is located on one polarization and the set of frequencies 602 is located on the other polarization. It is preferred that the polarizations of frequency set 601 and frequency set 602 are orthogonal to each other to minimize the possibility of interference between antennas operating at the same frequency but of different polarizations, as will be discussed further below. The polarization may be horizontally and vertically aligned, or left and right diagonal aligned, but is not limited to these ways.

It should be understood that although the following discussion explores frequency reuse patterns for 8 frequencies and two polarizations, the systems and methods of the present invention are not limited to 8 frequencies and 2 polarizations. The principles relating to frequency reuse patterns disclosed herein are equally applicable to the case where there are more than 8 frequencies available to a frequency reuse pattern communication system using the system and method of the present invention.

Fig. 6B depicts 8 cells, such as the cell shown in fig. 2A, where each cell is divided into 4 substantially non-overlapping sectors of 90 °. The hub of each cell has at least one antenna per sector, e.g., hub 105 shown in fig. 2B. As shown in fig. 6B, the reverse sectors of the cell operate on the same frequency/polarization assignment. Taking cell 610 as an example, sectors 601A and 601D operate on frequency/polarization 601A, while sectors 610B and 610C operate on frequency/polarization 602T. Although only such sector assignments are shown for cell 610, it should be understood that such sector assignments are applicable to each cell and are applicable throughout the specification and drawings. Since there are 8 frequencies and 2 polarizations per frequency as shown in fig. 6A, there are 16 unique available frequency/polarization sector assignments, or "degrees of freedom". In frequency reuse schemes, it is important to minimize adjacent channel and co-channel interference in order to maximize the "distance" between frequency/polarization sector assignments in a cell, i.e., to prefer maximum frequency spacing and orthogonal polarization assignments. In addition, for an adaptive time division duplex system ("ATDD"), maximization of the frequency separation can minimize coupling problems associated with the use of independent dynamically asymmetric frames within a cell. A 16 degree of freedom assignment pattern as shown in fig. 6A is preferred because this pattern results in the greatest "distance" between sector assignments for the cells. The system and method of the present invention contemplates the use of other 16 degree of freedom assignment patterns.

With the sector assignment pattern discussed above, if each 16 sector assignment or 16 degrees of freedom is used at once, there may be 8 unique "cell types". Each cell in fig. 6B is a unique cell type. These 8 cell types will be arranged in a particular manner to minimize co-channel and adjacent channel interference while achieving maximum operating area coverage for the communication system having the frequency/polarization assignment of fig. 6A.

Focusing now on fig. 7, a portion of a multi-cell frequency reuse pattern is described. As shown, the 16-cell 4 × 4 rectilinear grid 710 is composed of 42 × 2 subgroups, i.e., 701 and 704. Referring to the orientation of fig. 7, the 16-cell grid 710 can be repeated in both the vertical and horizontal directions so that the coverage area can be larger than the area covered by one instance of the grid 710. The cells are arranged in grid 710 such that each cell can occupy a unique row and column position, with all cells in the bottom row of fig. 7 being in designated row 720 and all cells in the left-most column of fig. 7 being in designated column 730. The cells are arranged in a 16-cell rectilinear grid 710 such that row and column adjacent cells are tangent, but diagonally adjacent cells are not. The designation of rows and columns is arbitrary and is used only to facilitate an accurate description of the arrangement of cells in the pattern. Such row and column designations are not part of the present invention and therefore should not be construed as limiting the invention in any way.

Referring now to fig. 8, a 4-cell subgroup 703 located in the lower left quadrant of the rectilinear grid 710 of fig. 7 is depicted. Each of the four cells in the small group of cells 703 is the only one of the 8 cell types discussed above and illustrated in fig. 6B. Cell 650 is tangent to its row and column neighbors, i.e., cell 650 is tangent to cell 610 and cell 660. Cells 610, 620, 650 and 660 are positioned in cell subgroup 703 so that the polarization of the facing cells is not the same for row and column neighbor cells. For example, sector 650B in cell 650 is one polarization and its opposite sector in row-adjacent cell 660, sector 660A, is the other polarization (see both polarizations in fig. 6A). By observing fig. 7 and 8, it can be seen that for 4 cell subgroups 701 and 704, the polarization of the opposite cells of the row and column neighbor cells are different. This way of locating cells within a small group minimizes co-channel and adjacent channel interference as discussed above.

Referring again to fig. 7, and focusing now on the cell subgroup 704, each of the 4 cells in the cell subgroup 704 is the only one of the 8 cell types discussed above and shown in fig. 6B. In addition, the cell type of each cell in the cell group 704 is different from the cell type used in the cell group 703. In other words, among the 8 cell types shown in fig. 6B, 4 cell types are used in the cell group 703 and the other 4 cell types are used in the cell group 704. The positioning of the cells in the small group of cells 704 is similar to the positioning of the cells in the small group of cells 703 discussed above, i.e., the polarization of the facing cells of the row and column neighbor cells are not the same. In addition, and preferably for cells 620, 660, 630 and 670, the polarization of the cells opposite the row neighbor cells is different, as shown in fig. 7.

Having discussed the positioning and arrangement of cells in the 4 cell groups, it should be noted that there is a relationship between cells in cell groups 703 and 702, and also between cells in cell groups 704 and 701. Referring to cell groups 703 and 702 in fig. 7, it can be seen that the same 4 cell types appear in each cell group and that the cells are arranged in the same manner in each cell group, i.e., cell 650 in cell group 703 is the same cell type as cell 650S in cell group 702. However, the frequency/polarization assignments for each cell have been exchanged between the reverse sector pair. However, for cell 650 in cell group 703, the upper right and lower left sectors are the first frequency/polarization combination, and the same first frequency/polarization combination occurs for the upper left and lower right sectors of cell 650S in cell group 702. This is also the case for each cell in the subgroups 703 and 702. Another way to observe this relationship is that the cells in the cell group 702 have been rotated 90 deg. from the direction of the cells in the cell group 703. Likewise, the cells in cell groups 704 and 701 are related in the same manner.

The reason for changing the direction of the cells between cell subgroups 703/702 and 704/701 is to minimize co-channel interference between sectors of cells of the same cell type. If, for example, cell 650S is in the same direction as cell 650, the facing sector 650A of cell 650 and sector 650SC of cell 650S will operate on the same frequency with the same polarization. If the cell radius is designated as "R", the distance between the hubs of cells 650 and 650S isThis distance is not sufficient to prevent co-channel interference. Switching frequency/polarization to the reverse sector helps overcome the problem of insufficient distance between hubs. With the frequency reuse scheme of FIG. 7, the distance between hubs that operate at the same frequency/polarization for opposite sectors isThis is 2 times the distance of the previous example. The pattern described above for the 4 x 4 rectilinear grid 710 may be repeated in both the horizontal and vertical directions to provide coverage for an area larger than the grid 710. As shown in fig. 7, the rows and columns of cells are repeated to illustrate the perspective of horizontal and vertical repeatability. It should be understood that the present invention is not limited to the particular number of cells shown in fig. 7, nor to a particular cell type assignment or sector direction. It is considered to be within the scope of this patent that a repeatable linear grid utilizing the concepts described above.

Turning now to fig. 9, a different cell description, referred to herein as shift and squish "mode, is depicted. As can be seen in fig. 7, the repeatable pattern of the rectilinear grid 710 causes a relatively large dead space to occur between the cells. The displacement and squeeze mode 910 eliminates most of this interstitial quiet zone. As with the rectilinear grid 710, the displacement and extrusion pattern 910 contains two 16 cells, each of 8 cell type. The next two rows of cells in the shift and squeeze pattern 910, similar to the next two rows of cells in the straight grid pattern 710, are made up of one 8-cell type as shown in fig. 6B. Likewise, the upper two rows of cells in the shift and squeeze pattern 910 are also made up of another set of one 8-cell type that is the same as the lower two rows, similar to the upper two rows of cells being made up of another set of one 8-cell type that is the same as the lower two rows in the straight grid pattern 710. However, unlike the straight grid 710, the two upper rows of cells of the shift and squeeze pattern 910 are not aligned in the same relative direction as the two lower rows of cells within the shift and squeeze pattern 910. For example, the cells 901-904 are arranged in a left-to-right order as 901/902/903/904, while the corresponding cells 901S-904S are arranged from left to right as 904S/901S/902S/903S. The cells in the other two rows of the grid 910 also maintain the same relationship. In addition, the frequency/polarization assignments for the two pairs of reverse sectors in the cell corresponding to the cell type are also exchanged.

The shifting and pressing pattern 910 may be repeated as shown in fig. 9. The 16 cells in this pattern are arranged such that no one cell is tangentially adjacent to two cells of the same cell type in either direction. This relationship is valid because this pattern is repeatable as shown in fig. 9.

The spacing between hubs in shifted and squeezed mode 910 for cells with opposite sectors operating at the same frequency/polarization, such as cells 901 and 911, is approximately 10R, which is approximately 88% of the distance between hubs in straight grid 710 with opposite sectors operating at the same frequency/polarization. The distance between the hubs of cells 901 and 911 should be sufficient to prevent co-channel interference.

Referring now to fig. 10, a portion of another multi-cell frequency reuse pattern is depicted. This 16-cell 4 × 4 rectilinear grid 1010 is composed of 42 × 2 subgroups, 1001 and 1004. Referring to the orientation of fig. 10, the 16-cell grid 1010 is repeatable vertically and horizontally to cover an area larger than that covered by one instance of the grid 1010. The cells in grid 1010 are arranged similarly to the cells of grid 710 of fig. 7, such that each cell occupies a unique row and column position and such that row and column adjacent cells are tangential, but such that diagonally adjacent cells are not.

Fig. 11A depicts a set of 8 available frequency channels 1100 for a communication system where two polarizations of available frequency are available, similar to the set of frequencies 600 in fig. 6A. Of the 16 frequency/polarization degrees of freedom of the set 1100, a set of 8 frequency/polarization degrees of freedom 1103 and another set of 8 frequency/polarization degrees of freedom 1104 are depicted. The set of degrees of freedom 1103 is used in the frequency reuse mode of fig. 10. The set of degrees of freedom 1104 does not have to fill the cells of the frequency reuse pattern of fig. 10, which is reserved for possible future use, as will be described below.

Fig. 11B illustrates 8 cell types used in the frequency reuse pattern straight grid 1010 of fig. 10. As shown in fig. 11B, each sector of a particular cell of each 8 cell type operates at a unique frequency/polarization assignment relative to the other sectors of the cell. For each cell type, there is one pair of adjacent sectors operating in a first polarization and another pair of adjacent sectors operating in a second of the two possible polarizations. Taking cell 1110 as an example, each sector 1110A-1110D operates at a different frequency/polarization from each other. Since 4 frequencies and two available polarizations per frequency are used as shown in fig. 11A, there are 8 available degrees of freedom. The linear grid 1010 is populated with 8 different cell types due to limitations discussed below.

Referring now to fig. 12, a 4-cell subgroup 1003 located in the lower left quadrant of the rectilinear grid 1010 of fig. 10 is depicted. In cell subgroup 1003, each of the 4 cells is the only one of the 8 cell types discussed above and illustrated in fig. 11B. In addition, in 4-cell subgroup 1003, the opposite sector of each cell is the same frequency/polarization regardless of whether the cell is row and column adjacent or diagonally adjacent. For example, as shown in fig. 12, 1110D, 1120C, 1150B, and 1160A are all assigned the same frequency/polarization for all 4 cell center-facing sectors. In addition, sector 1110C of cell 1110 and sector 1150A of cell 1150 are face-to-face and have the same frequency/polarization assignment. For the following sectors: 1150D and 1160C, 1160B and 1120D, and 1110B and 1120A, the same applies. Furthermore, the reverse sectors of the diagonal neighbor cells in the 4-cell subgroup 1003 have the same frequency/polarization assignment: sectors 1150C and 1120B, and sectors 1110A and 1160D. These frequency/polarization assignments allow the pattern of the rectilinear grid 1110 to be repeated, as can be seen in fig. 10, while minimizing co-channel and adjacent channel interference.

Referring again to fig. 10, attention is now directed to a small group of cells 1004, in which small group of cells 1004 each of the 4 cells is the only one of the 8 cell types discussed above and shown in fig. 11B. In addition, the cell type of each cell in the cell group 1004 is different from the cell type used in the cell group 1003. In other words, among the 8 cell types depicted in fig. 11B, 4 cell types are used for the cell group 1003, and the other 4 cell types are used for the cell group 1004. The positioning of the cells in the subgroup of cells 1004 is similar to the positioning of the cells in the subgroup of cells 1003 discussed above: the facing sectors of each cell in 4-cell subgroup 1004 have the same frequency/polarization regardless of whether the cells are row and column adjacent or diagonally adjacent.

Having discussed the positioning and arrangement of cells in the 4-cell subgroup above, it should be noted that there is a relationship between the cells of the cell subgroups 1003 and 1002, and also between the cells of the cell subgroups 1004 and 1001. Referring to cell groups 1003 and 1002 in fig. 10, it can be seen that the same 4 cell types are present in each of these cell groups, and the arrangement of the cells and the sector locations within the cells are the same in each cell group, i.e. cell 1150 in cell group 1003 is the same cell type as cell 1150S in cell group 1002. Likewise, the cells in cell groups 1004 and 1001 are related in the same way.

The linear grid 1010 may also be repeated in the horizontal and vertical directions, similar to the repeatability of the linear grid 710. It should be noted that the inward sectors of the 4 cells of any 2 x 2 grid have the same frequency/polarization assignment within the repeatable pattern. This arrangement synchronizes the inward sectors, as has been fully described above.

Any two facing sectors having the same frequency/polarization assignment but not adjacent facing sectors are spaced apart by a distance ofThis distance should be sufficient to prevent co-channel interference between non-adjacent opposing sectors having the same frequency/polarization assignment. If co-channel interference is present, the two sets of 4 cells with interfering non-adjacent opposing sectors may also be synchronized to avoid co-channel interference problems.

Referring to FIG. 13, a rectilinear grid 1310 is illustrated that is similar to the rectilinear grid 1010 of FIG. 10. However, grid 1310 includes a sector coverage of these sectors, referred to herein as overlapping sectors. For this reason, the capacity of the system is not sufficient to support the user demand in these sectors. Increased sector coverage represents increased antennas and corresponding circuitry at the hub of the cell where coverage exists. Increased sector coverage is generally not a simple replacement for overlapping sectors. The increased coverage works differently at frequencies than overlapping sectors but with the same polarization. This configuration enables sharing of protection or redundancy devices between overlapping and coverage sectors. The size of the coverage sector is typically equal to or smaller than the size of the overlapping sector. As shown in fig. 13, the overlapping sectors are 45 sectors, but the system and method of the present invention is not limited to 45 sectors. In addition, fig. 13 illustrates a coverage sector 1390 added to one of each of the sectors of 4 cells 1-4, which is merely one example of the use of a coverage sector. The system and method of the present invention is not limited to adding coverage sectors to a small group of 4 opposite sectors, but more or less coverage sectors may be added according to the needs of the user. Adding coverage sectors to all 4 facing sectors of 4 neighboring cells enables the added 4 coverage sectors to be synchronized in a manner similar to the synchronization of the 4 underlying overlapping sectors. Naturally, less than 4 coverage sectors may also be added and synchronized.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims (68)

1. A repeatable frequency reuse pattern in a wireless communication system, comprising:

16 substantially circular cells of approximately the same radius, arranged in a 4 x 4 grid so that no two cells substantially overlap and each cell is substantially tangent to its adjacent rows and columns of cells, each cell containing a hub having 4 antennas, each antenna serving one of 4 substantially non-overlapping 90 ° sectors and capable of communicating on each 8 frequencies and on any two polarizations of each frequency, so that for each hub, a set of inverted 90 ° sectors communicates on one of said 8 frequencies and on one of said polarizations and another set of inverted 90 ° sectors communicates on a different one of said 8 frequencies and on another of said polarizations;

8 cell types, wherein each cell type communicates over a unique frequency combination;

first and second 4-cell subgroups, each subgroup comprising a 2 x 2 grid of cells such that,

said first 4-cell subgroup comprising 4 different ones of said 8 cell types, said cells being arranged in such a way that facing sectors of row and column neighbouring cells have different polarizations, an

Said second 4-cell subgroup comprising 4 further different cell types, said cells being arranged in such a way that opposite sectors of row and column neighbouring cells have different polarizations;

third and fourth 4-cell subgroups, each subgroup comprising a 2 x 2 grid of cells such that,

the third 4-cell subgroup comprises the same 4-cell types as the first subgroup, wherein frequency and polarization assignments are exchanged between pairs of reverse sectors of each cell, the 4 cells are arranged in the same manner as the cells of the first subgroup, and

said fourth 4-cell subgroup comprises the same 4-cell types as said second subgroup, wherein frequency and polarization assignments are exchanged between pairs of reverse sectors of each cell, said 4 cells being arranged in the same manner as the cells in said second subgroup;

wherein said 4 subgroups of cells are arranged in said 4 x 4 grid such that said first and third subgroups of cells are non-row and column adjacent, and facing cells between row and column adjacent subgroups use different frequencies.

2. The pattern of claim 1 wherein the polarizations are mutually orthogonal.

3. The pattern of claim 1 wherein the communication system is a time division duplex system.

4. The pattern of claim 3 wherein the communication system is an adaptive time division duplex system.

5. The pattern of claim 4 wherein the 8 frequencies are in the millimeter frequency range.

6. The pattern of claim 5 wherein the 8 frequencies are each in the range of 10-60 GHz.

7. The pattern of claim 1, wherein the cells are not synchronized.

8. The pattern of claim 7 wherein the sectors within the cell are not synchronized.

9. The pattern of claim 1 wherein said 16 cells are generally circular, approximately the same radius, and are arranged in a 4 x 4 grid such that the distance between the centers of any two horizontally and any two vertically adjacent cells is approximately twice the radius of the cell.

10. A horizontally and vertically repeatable cell pattern in a multi-cell pattern forming a rectilinear grid in a communication system, wherein each cell is divided into 4 90 sectors, each sector having at least one antenna, whereby each antenna can operate in one of two polarization modes for each communication frequency, wherein each cell uses two frequencies and adjacent sectors of each cell alternate in frequency and polarization.

11. The pattern of claim 10 wherein the polarizations are mutually orthogonal.

12. The pattern of claim 11 wherein the grated diagonally alternating cells are rotated 90 degrees relative to each other.

13. The pattern of claim 12 wherein the number of frequencies is 8.

14. The pattern of claim 13, wherein each cell is one of 8 cell types, whereby each cell type employs a unique combination of frequency and polarization.

15. The pattern of claim 14, wherein each cell type is repeated once within the pattern.

16. The pattern of claim 15 wherein the communication system is a time division duplex system.

17. The pattern of claim 16 wherein the communication system is an adaptive time division duplex system.

18. The pattern of claim 17 wherein the 8 frequencies are in the millimeter frequency range.

19. The pattern of claim 18 wherein the 8 frequencies are each in the range of 10-60 GHz.

20. In a horizontally and vertically repeatable cell pattern of a multi-cell pattern forming a rectilinear grid in a communication system, wherein each cell is divided into 4 90 sectors, each sector having at least one antenna, whereby each antenna is operable in one of two polarization modes for each communication frequency, a method for reducing co-channel interference comprising the steps of:

(a) alternating adjacent sectors of each cell in frequency and polarization; and

(b) at least one pair of alternating diagonal cells within the grid are relatively shifted by 90.

21. The pattern of claim 20 wherein adjacent channel interference is reduced.

22. The pattern of claim 20 wherein the polarizations are mutually orthogonal.

23. The pattern of claim 22 wherein the number of frequencies is 8.

24. The pattern of claim 23, wherein each cell is one of 8 cell types, whereby each cell type employs a unique combination of frequency and polarization.

25. The pattern of claim 24, wherein each cell type is repeated once within the pattern.

26. The pattern of claim 22 wherein the communication system is a time division duplex system.

27. The pattern of claim 26 wherein the communication system is an adaptive time division duplex system.

28. The pattern of claim 27 wherein the 8 frequencies are in the millimeter frequency range.

29. The pattern of claim 28 wherein the 8 frequencies are each in the range of 10-60 GHz.

30. In a 16-cell pattern arranged in a 4 x 4 grid of a multi-cell pattern forming a rectilinear grid in a communication system, wherein each cell is divided into 4 90 sectors, each sector having at least one antenna, whereby each antenna is operable in one of two polarization modes for 8 communication frequencies, whereby for each hub, a set of reverse 90 sectors communicates on one of said 8 frequencies and on one polarization, and another set of reverse 90 sectors communicates on a different one of said 8 frequencies and on another polarization, a method of reducing co-channel interference comprising the steps of:

(a) dividing the 16 cells into 4 cell subgroups, whereby each subgroup comprises a 2 x 2 grid of cells;

(b) providing 8 cell types, wherein each cell type communicates over a unique frequency combination;

(c) providing a first 4-cell subgroup comprising 4 different ones of said 8 cell types, said cells being arranged in such a way that facing sectors of row and column adjacent cells have different polarizations;

(d) providing a second 4-cell subgroup comprising 4 further different cell types, said cells being arranged in such a way that facing sectors of row and column adjacent cells have different polarizations;

(e) repeating said first and second subgroups of cells diagonally within said 16-cell pattern;

(f) the frequency and polarization assignments in the sectors of each cell of the repeated first and second cell subsets are rotated by 90 deg. with respect to the frequency and polarization assignments in the sectors of the first and second cell subsets.

31. The pattern of claim 30 wherein adjacent channel interference is reduced.

32. The pattern of claim 30 wherein the polarizations are mutually orthogonal.

33. The pattern of claim 32 wherein the communication system is a time division duplex system.

34. The pattern of claim 33 wherein the communication system is an adaptive time division duplex system.

35. The pattern of claim 34 wherein the 8 frequencies are in the millimeter frequency range.

36. The pattern of claim 35 wherein the 8 frequencies are each in the range of 10-60 GHz.

37. A frequency reuse pattern in a wireless communication system comprising 16 substantially circular cells of approximately the same radius arranged in a repeatable 4 x 4 grid forming a parallelogram such that the edge of any one cell is tangent to the edges of 6 other cells, wherein each cell contains a hub having 4 antennas, wherein each antenna serves one of 4 substantially non-overlapping 90 ° sectors and is capable of communicating at every 8 frequencies and at any two polarizations of each frequency, such that for each hub a set of inverted 90 ° sectors communicates at one of the 8 frequencies and at one polarization and another set of inverted 90 ° sectors communicates at a different one of the 8 frequencies and at another polarization, said pattern comprising:

8 cell types, wherein each cell type communicates over a unique frequency combination;

a first 4-cell subgroup consisting of 4 different ones of said 8 cell types, said cells being arranged such that the centers of each cell are collinear and the edges of adjacent cells are tangent, such that facing sectors of adjacent cells have different polarizations;

a second 4-cell subgroup comprising 4 further different cell types, said cells being arranged such that the centres of each cell are collinear and the edges of adjacent cells are tangent, such that facing sectors of adjacent cells have different polarizations, and said first and second cell subgroups being arranged such that each cell of each subgroup is adjacent to and tangent to at least one cell of the other subgroup;

a third 4-cell subgroup comprising the same 4-cell types as said first subgroup, wherein frequency and polarization assignments are exchanged between pairs of reverse sectors of each cell, said 4 cells being arranged such that the centers of each cell are collinear and the edges of adjacent cells are tangent, whereby said second and third cell subgroups are arranged such that each cell of each subgroup is adjacent and tangent to at least one cell of the other subgroup, and cells not adjacent to a cell in the third subgroup are also adjacent to cells in the first subgroup having a frequency combination corresponding to said cell in the third subgroup;

a fourth 4-cell subgroup comprises the same 4-cell types as said second subgroup, wherein frequency and polarization assignments are exchanged between pairs of reverse sectors of each cell, said 4 cells being arranged such that the centers of each cell are collinear and the edges of adjacent cells are tangent, whereby said third and fourth cell subgroups are arranged such that each cell of each subgroup is adjacent and tangent to at least one cell of the other subgroup, and cells in the second subgroup which are not adjacent to cells in the fourth subgroup are also adjacent to cells in the second subgroup having a frequency combination corresponding to said cells in the fourth subgroup.

38. The pattern of claim 37, wherein said 16 cells are generally hexagonal in shape.

39. The pattern of claim 37, wherein the pattern repeats in the horizontal and vertical directions.

40. The pattern of claim 37, wherein the polarizations are mutually orthogonal.

41. The pattern of claim 40 wherein the communication system is a time division duplex system.

42. The pattern of claim 41 wherein the communication system is an adaptive time division duplex system.

43. The pattern of claim 42 wherein the 8 frequencies are in the millimeter frequency range.

44. The pattern of claim 43 wherein the 8 frequencies are each in the range of 10-60 GHz.

45. The pattern of claim 44, wherein the cells are not synchronized.

46. The pattern of claim 45 wherein the sectors within the cell are unsynchronized.

47. A frequency reuse pattern in a wireless communication system comprising 16 cells arranged in a 4 x 4 grid containing 4 sub-clusters arranged in 4 cells of a 2 x 2 grid, wherein each cell contains a hub having 4 antennas, wherein each antenna serves one of 4 substantially non-overlapping 90 ° sectors and is capable of communicating at every 8 frequencies and at any two polarizations of each frequency, wherein for each hub each sector communicates at a different frequency, wherein two adjacent sectors communicate at one polarization and two other adjacent sectors communicate at another polarization, the pattern comprising:

8 cell types, wherein each cell type communicates over a unique combination of frequencies, whereby the 8 cell types are comprised of 4 frequencies located in said one polarization and 4 frequencies located in said another polarization;

a first sub-cluster comprising 4 different ones of said 8 cell types, said cells being arranged such that facing sectors of adjacent cells communicate on the same frequency and the same polarization, an

The second sub-cluster contains 4 other different cell types arranged such that facing sectors of adjacent cells communicate on the same frequency and the same polarization;

a third sub-cluster identical to the first sub-cluster;

a fourth sub-cluster identical to the second sub-cluster;

wherein the sub-clusters are arranged in the 4 x 4 grid such that the first and third sub-clusters are not adjacent and the facing cells between adjacent sub-clusters communicate on the same frequency and the same polarization.

48. The pattern of claim 47, wherein the polarizations are mutually orthogonal.

49. The pattern of claim 47 wherein the communication system is a time division duplex system.

50. The pattern of claim 49 wherein the communication system is an adaptive time division duplex system.

51. The pattern of claim 50 wherein the 8 frequencies are in the millimeter frequency range.

52. The pattern of claim 51 wherein the 8 frequencies are each in the range of 10-60 GHz.

53. The pattern of claim 52, wherein the cells are synchronized.

54. The pattern of claim 53 wherein adjacent sectors communicating on the same frequency and the same polarization are synchronized.

55. The pattern of claim 54, wherein said adjacent sectors communicate with a universal dynamic asymmetric synchronization.

56. The pattern of claim 47 comprising at least one additional sector communicating on a frequency and polarization combination of said 8 frequencies and two polarizations not used in said pattern, whereby said additional sector overlies at least one sector in said pattern having a similar polarization to that of said additional sector.

57. The pattern of claim 56 wherein the additional sectors are 90 ° sectors.

58. The pattern of claim 56 wherein the additional sectors are 45 ° sectors.

59. A method of reducing co-channel interference in a horizontally and vertically repeatable cell pattern of a multi-cell pattern forming a rectilinear grid in a communication system, wherein each cell includes a hub having 4 antennas, wherein each antenna serves one of 4 substantially non-overlapping 90 ° sectors, and wherein each communication frequency used in said communication system is capable of communicating in one of two polarization modes, such that for each hub a set of inverted 90 ° sectors communicates on one said communication frequency and on one said polarization, and another set of inverted 90 ° sectors communicates on a different said communication frequency and on another said polarization, the method comprising the steps of:

(a) providing 8 cell types, wherein each cell type comprises a unique combination of the two frequency and polarization sets;

(b) providing two cell sub-clusters, each of four cells arranged in a 2 x 2 grid, wherein a first sub-cluster comprises 4 cells, each cell being a different one of said 8 cell types, and wherein a second sub-cluster comprises 4 cells, each cell being a different one of another 4 cell types;

(c) rotating the sub-clusters horizontally and vertically within the multi-cell pattern; and

(d) each pair of alternating diagonal cells within the multi-cell pattern is relatively changed by 90 °.

60. The method of claim 59, wherein adjacent channel interference is reduced.

61. The method of claim 59, wherein the polarizations are mutually orthogonal.

62. The method of claim 61, wherein the number of frequencies is 8.

63. The method of claim 61, wherein the frequency number is at least 8.

64. The method of claim 63, wherein each cell type is repeated once within the pattern.

65. The pattern of claim 61 wherein the communication system is a time division duplex system.

66. The pattern of claim 65 wherein the communication system is an adaptive time division duplex system.

67. The pattern of claim 66 wherein the 8 frequencies are in the millimeter frequency range.

68. The pattern of claim 67 wherein the 8 frequencies are each in the range of 10-60 GHz.