GB2343813A

GB2343813A - Sectored digital data distribution

Info

Publication number: GB2343813A
Application number: GB9920169A
Authority: GB
Inventors: Michael J Paolini
Original assignee: EagleView Technologies Inc
Current assignee: EagleView Technologies Inc
Priority date: 1998-09-03
Filing date: 1999-08-25
Publication date: 2000-05-17
Also published as: GB9920169D0; DE19940067A1; RO120230B1

Abstract

A High speed wireless digital signal distribution and communication system includes a matrix array of a plurality (M) of sectors, each of which includes a plurality (N) of point to point rf modules, which have random frequency hopping capabilities. By the use of this array the effective data-transmission capacity is increased by N x M over the capacity of a single point to point rf mobile. Each of the modules is able to communicate digital data packets including LAN address data over a wireless rf link, to an associated remote wired LAN.

Description

2343813 PROCESS OF MAKING A MATRIX ARRAY OF ANTENNAS AND POINT TO POINT

EQUIPMENT

BACKGROUND OF THE INVENTION

The present invention relates generally to digital communication, and more particularly to wireless digital communication.

In recent years, particularly since the introduction of the Ethernet standard, the use of local area networks (IANs) has become widespread, such as to connect computers in offices located at different locations in a building or to connect a number of PCs to a common data source such as a file server or work station. A LAN typically includes a plurality of nodes commonly in the form of a series of PCs connected, such as by means of a cable, to one another through appropriate interfaces or hubs, in a manner that allows any of the PCs in the network to transmit and/or receive digital data to a selected one or more of the other PCs in the network, and also to communicate over the cable to high-capacity devices such as work stations and file servers.

In order to create a LAN in an environment in which the interconnections among the PCs by means of cable, Ethernet wiring, or other type of conductor is not practical, as is the case in a mobile location or in a temporary office, wireless networks are used to effect data communication to the various PCs in the network through a rf wireless communication link. Wireless data communication links are also currently in use to link a computer network with the Internet to allow the PCs in the network to access the Internet.

Data transmission systems that are capable of providing wireless digital communication to a wired LAN are currently offered for sale, such as by BreezCom wireless Communications. The data-transmitting capacity and speed of these and other currently available known wireless data transmission systems is, however, relatively low; only one access node can provide communication to each remote data reception location. In view of the relatively high cost of wireless 1ANs as compared to wired LANS, the limited data transmission capacity of the known wireless LAN systems has thus far limited their use.

The recent widespread use of the Internet has further increased the demand for high-speed two-way access in digital communications to and from PCs connected in a IAN.

Since the access nodes on the Internet communication link are costly, it is desirable for the maximum number of users should be able to engage in two-way communication with a single access node or access point. Highspeed user connections to the access node on a wired basis are, however, as noted, relatively expensive as opposed to a wireless solution. There is thus a current need for a wireless digital communication system in which increased data-transmission capacity can be achieved at a relatively low cost.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of the present invention to provide a wireless digital communication system having a relatively high data transmission capacity.

It is a further object of the present invention to provide a high-capacity digital transmission system that includes a plurality of two-way transmission modules and yet maintains the EIRP of the system very close to that of individual point-to-point modules.

In accordance with the present invention, a digital data communication system includes a matrix array made up of a plurality (M) of sectors, each of which receives digital data packets including LAN address data from a data source. Each of the M sectors constitutes one portion of up to a 3600 horizontal circle associated with central radiation locations that communicate over the air to a plurality of remote LANs. Each of the N modules receives and accepts a digital data packet addressed to it from a signal source. The module modulates its received data packet onto an rf carrier. The output of the module, along with the digital modulated rf signals from the other modules in the sector, are applied to the N inputs of an N-way combiner, the output of which is coupled to an antenna, from which the digital data packets modulated onto as many as N rf carriers are transmitted over the air to the remote LANs.

By the use of this matrix array, the effective radiated capacity of the system is increased over that of a single point-to-point module by a factor of MxN. In a presently preferred embodiment of the invention, the value of M is between two and forty, and the value of N is between two and eight. It is possible with this matrix arrangement to achieve a MxN or up to 320-fold increase of data-transmission capacity.

Commercially available frequency hopping spread spectrum (FHSS) units produce a pseudorandom sequence of different frequencies, known as frequency hopping, typically over eighty discrete frequency channels. These units have an EIRP limitation of approximately four watts so that under FCC rules they can be used on an unlicensed basis. The above-mentioned BreezCom wireless LAN system, for example, employs such FHSS units. In the embodiment of the present invention herein described, each of the N point-to-point modules in the M sectors includes a FHSS unit, at which the data packet specifically addressed to that module is modulated onto the varying or hopping carrier frequency.

As long as N is small compared to the total number of hopping channels at the point-to-point modules in each sector, there is no effective increase in the EIRP of the system. For a value of N equal to eight or less, there would be less than a ten percent increase in power, so that the EIRP of any of the point-to-point modules need only be reduced by one decibel or less to comply with existing EIRP regulations.

DESCRIPTION OF THE DRAWINGS

To the accomplishment of the above and to such further objects as may hereinafter appear, the prevent invention relates to a digital wireless communication system, substantially as defined in the appended claims, and as described in the following detailed description of a presently preferred embodiment, as considered with the accompanying drawings in which:

Fig. 1 is a schematic block diagram of a digital communication system in accordance with an embodiment of the invention; and Fig. 2 is a more detailed schematic block diagram of a single sector of the system of Fig. 2; Fig. 3 is a schematic block diagram illustrating a transmission path from one sector of the system of the invention to a LAN; and Fig. 4 illustrates one possible arrangement of a plurality of sectors in a matrix array in accordance with the communication system of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Considered broadly, the digital transmission system of the invention comprises a plurality (M) or sectors arranged in an array or matrix which may cover all or part of a 360 circular orientation. Each of the M sectors includes a plurality (N) of point-to-point transmission modules, each of which is capable of communicating over a wireless rf link with an associated remote wired LAN. That is, as described in greater detail below, each of the N modules in any of the M sectors is uniquely associated with, that is, is able to communicate with, one remote LAN. Each module in each sector thus constitutes an access node or access point for a particular LAN.

As illustrated in Fig. 1, each sector 10, to 10n includes an N-way combiner 12 coupled to an output of each of the N point- to-point modules 40 in the sector, and an N-way splitter 14 connected to an input of each of the N modules 40 in that sector. As illustrated schematically in Fig. 3, the output of N-way combiner 12 is applied to a transmitting antenna 16, and an input of the N-way splitter 14 receives a signal from a receiving antenna 18. Antenna 16, as also described in greater detail below, transmits over the air a multi-frequency r.f. signal modulated with one or more digital data packets that include address information relating to a specified one or more (up to N) of the remote LANS.

The signal from antenna 16 is received by an antenna 20 located at the site of the remote IANs that are to communicate with the modules 40 in that sector. The signal received by antenna 20 is applied to a wireless bridge receiver 22 that receives and demodulates the received rf modulated digital signals, selects one or more of the demodulated data packages in accordance with the address data contained in the packet, and applies the received digital signal to an input of an Ethernet hub 24.

The output of hub 24 is connected, such as by means of a cable, to the appropriately addressed one of a plurality (three of which are shown in Fig. 1) of LAN users associated with the receiver 22.

Any of the LAN users may communicate back to the system, such as to make an Internet request, or otherwise to achieve two-way wireless digital communication by applying signals through the hub 24 to the wireless bridge receiver 22, where the digital signal from the LAN is modulated onto a carrier, which is then applied to a transmitting antenna 26. The latter communicates over an rf over-the-air link to the receiving antenna 18 at the sector 10n containing the module 40 that is associated with the requesting LAN.

Referring again to Fig. 1, digital data in, for example, 10OBaseT digital form is routed and distributed selectively to the 1OBaseT hubs 42 in each of the M sectors by a NT server-router 32, which may be connected, for example to the Internet. It is to be understood that the digital input signals may also be derived from a high speed fiber optic or satellite signal. Moreover, instead of an NT-server/router, any other server or router may be used in the system of the invention, and the server/router may, if desired, include Internet service provider (ISP) capabilities such as web hosting and e-mail.

Router 32 in a known way converts the 10OBaseT data to the lower frequency 1OBaseT data, and based on the header address included in the input data packet, it directs or routes the data packet to appropriate (addressed) one of the sectors 10 along one of data bus lines 361, 362,.. - 36m. only one of the sectors 10 will receive data packets from router 32 at any given time in accordance with the data packet header address.

The 1OBaseT data derived from router 32 is applied to a 1OBaseT hub 42, which has N outputs connected respectively to each of the N modules 40 in that sector, and directs the data packets to all of the N modules.

However, only one of the modules 40 in that sector can accept that data package as determined by the header address in the data packet, which may be detected by a hub interface (not shown) associated with each of the modules.

Each of the modules 40 preferably is a frequency hopping spread spectrum (FHSS) unit, which includes a radio-frequency rf oscillator in which the frequency is variable or able to "hop" between different rf frequencies in a pseudorandom manner at preset intervals of typically 0.25 second. Commercially available frequency hopping spread spectrum (FHSS) modules, which have this capability, shift rf frequency in a pseudorandom manner among 80 available rf channels. Each of these channels typically has a bandwidth of approximately 1.0 MHz and extend between a frequency of 2400 to 2401 MHz at the lowest frequency channel to a frequency of 2482.5 to 2483.5 HHz at the highest frequenc y channel.

The modules 40 also each include a modulator, which modulates the randomly varying rf frequencies with the 1OBaseT data package that is input to that module. The digital modulated rf signal, in which, as noted, the carrier frequency changes each 0.25 seconds, is applied to one of the inputs of the N-way combiner 12 on a line 44 from which this modulated rf signal is transmitted over the air to the wired bridge receiver 22, which, as described above, is then directed to the IAN associated with the data-transmitting module 40.

To receive digital data from the remote LAN, such as a request to the Internet, a digitally modulated rf signal is transmitted from the requesting LAN, received at N-way splitter 14, and directed to the corresponding or associated module 40 where the signal is demodulated to remove the LAN-transmitted digital packet. That data packet is then applied through the sector hub 42 to the server 32 from where it is applied to the signal source.

Fig. 2 illustrates, in somewhat greater detail, a single one of the M sectors 10. As therein shown, the sector includes a plurality (N), here shown for purposes of example as five, of frequency hopping point-to-point modules 40. The input of each of the modules is connected to one of the N outputs of a hub 42, which receives at its input the digital signal from the server 32 addressed to that sector. According to the address data combined in the hub output signal, that signal will be accepted by one of the modules 40-40n in that sector, and will be, as noted previously, modulated at that module onto an rf carrier at a frequency that varies periodically in a pseudo random manner in accordance with its frequency hopping protocol for that module. A corresponding frequency hopping protocol is utilized in the wireless bridge receiver 22 that is associated with the module.

Each of the N modules 40 in a sector is capable of receiving a digital packet from hub 42 that contains the address of the module, and is intended for transmission to the LAN associated with that particular module. Each module to which a data packet is thus addressed accepts that data packet and modulates it onto a randomly hopping or shifting rf carrier. The modulated output signals from the addressed modules are respectively applied to the associated inputs of the N-way combiner 12, from where they are transmitted by antenna 16 to the remote LAN locations. At those locations, the modulated rf carriers are respectively received and demodulated at the bridge receivers 22 associated with the datatransmitting module or access node. To this end, each of the bridge receivers have frequency hopping protocols that are comparable to those of their associated modules.

Because of the great number of the available different rf frequencies that may be at any one time generated in the frequency-hopping modules 40, it is highly unlikely that any of the up to N modulated rf inputs to the N-way combiner 12 will be at any one time at the same frequency. Accordingly, the transmitting antenna 16 in each of the sectors may transmit N different digital signals modulated onto a corresponding number of rf carriers at different frequencies to N remote LANs.

Request signals received from the remote IANs are received at the receiving antenna 18 and directed to the appropriately addressed module 40, where it is demodulated and applied through the hub 42 and router 32 to the signal source. In response to that request, a digital signal is then transmitted from a specified point-to-point module 40 associated with that requesting LAN from the signal source to the requesting LAN in the manner described above.

Fig. 4 illustrates one of the many possible arrangements of M sectors to provide high-capacity wireless digital data communication to a plurality of remote IANS. As shown in Fig. 4, eight (M) sectors 101-10m are arranged in a manner to establish a sector covering about 210. As described previously, each of these sectors can transmit a digital signal over the air to up to N (the number of modules in that sector) different remote IANs located in the communication path of the sector.

The data transmission capacity of each of the sectors 10 can be increased by horizontally and vertically crosspolarizing the transmission from the transmission antennas 16 in each sector. Vertically or horizontally polarized antennas typically have a discrimination sensitivity of between twenty to thirty decibels against their opposite polarization. This amount of discrimination is sufficient for an individual receiver to discriminate against a received signal of opposite polarization, even if the signal was on the same frequency. Thus all of the same rf carrier frequencies transmitted from each sector and described above can be used again on the opposite polarization, thereby doubling the capacity of the array, as desired.

It will thus be appreciated that the arrangement of the present invention of a matrix array of M sectors of rf digital data transmission each of which includes a plurality (N) of rf point-to-point modules, provides a high-capacity digital data distribution and communication system in which the data distribution capacity is increased, by a factor of MxN, times the capacity of a single point to point rf module. It will be further appreciated that although the digital data distribution and communication system of the invention has been herein described with reference to a presently preferred embodiment, variations and modifications may be made thereto without necessarily departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A wireless digital communication system comprising a first plurality (M) of sectors respectively located to transmit digital rf signals overthe-air to remotely located data-receiving stations, each of said first plurality of sectors including a second plurality (N) of rf modules, said second plurality of modules each having the capability of modulating a common digital input signal onto a rf carrier at a different frequency, whereby digital data may be transmitted from said modules to up to MXN remote data receiving locations.

2. The wireless communication system of claim 1, in which each of said N modules produces a rf carrier signal of a different frequency.

3. The wireless communication system of claim 2, in which each of said N modules includes a hub having an input receiving a digital input signal and N outputs respectively coupled to the inputs of said N modules.

4. The wireless communication system of claim 3, in which each of said M sectors also includes a transmitting antenna and a signal combiner having N inputs respectively coupled to the outputs of said N modules and an output coupled to said transmitting antenna.

5. The wireless communication system of claim 4, in which said M sectors each include a receiving antenna and a splitter having an input coupled to said receiving antenna and N outputs respectively coupled to each of said N modules in said sector.

6. The wireless communication system of claim 1, in which each of said N modules includes a hub having an input receiving a digital input signal and N outputs respectively coupled to the inputs of said N modules.

7. A wireless digital communication system substantially as hereinbefore described with reference to, and as illustrated in, the accompan ing drawings. Yi I

7. Thewireless communication system of claim 6, in which each of said M sectors also includes a transmitting antenna and a signal combiner having N inputs respectively coupled to the outputs of said N modules and an output coupled to said transmitting antenna.

8. The wireless communication system of claim 7, in which said M sectors each include a receiving antenna and a splitter having an input coupled to said receiving antenna and N outputs respectively coupled to each of said N modules in said sector.

9. A wireless digital communication system substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS:

1. A wireless digital communication system comprising a first plurality (M) of sectors respectively located to transmit digital rf signals over the-air to remotely located data-receiving stations, each of said first plurality of sectors including a second plurality (N) of rf modules, said second plurality of modules each having the capability of modulating, a common digital input signal onto a rf carrier at a different frequency, wherein each of said M sectors also includes a transmitting antenna and a signal combiner having N inputs respectively coupled to the outputs of said N modules and an output coupled to said transmitting antenna, whereby digital data is transmittable from said modules to up to MXN remote data receiving locations.

2. The system of claim 1, in which each of said N modules produces a rf carrier signal of a different frequency.

3. The system of claim I or 2, in which each of said N modules includes a hub having an input receiving a digital input signal and N outputs respectively coupled to the inputs of said N modules.

4. The wireless communication system as claimed in any preceding claim, in which each of said N modules includes a hub having an input receiving a digital input signal and N outputs respectively coupled to the inputs of said N modules.

5. The system as claimed in any preceding claim, in which each of said M sectors also includes a transmitting antenna and a signal combiner having N inputs respectively coupled to the outputs of said N modules and an output coupled to said transmitting antenna.

1 14 6. The system as claimed in any preceding claim, in which said M sectors each include a receiving antenna and a splitter having an input coupled to said receiving antenna and N outputs respectively coupled to each of said N modules in said sector.