GB2367215A - In a point to multipoint system establishing a reference frequency at the hub and transmitting it to all subscribers as a common reference - Google Patents
In a point to multipoint system establishing a reference frequency at the hub and transmitting it to all subscribers as a common reference Download PDFInfo
- Publication number
- GB2367215A GB2367215A GB0023484A GB0023484A GB2367215A GB 2367215 A GB2367215 A GB 2367215A GB 0023484 A GB0023484 A GB 0023484A GB 0023484 A GB0023484 A GB 0023484A GB 2367215 A GB2367215 A GB 2367215A
- Authority
- GB
- United Kingdom
- Prior art keywords
- frequency
- hub
- signal
- beacon
- radio
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W48/00—Access restriction; Network selection; Access point selection
- H04W48/08—Access restriction or access information delivery, e.g. discovery data delivery
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/24—Cell structures
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/10—Small scale networks; Flat hierarchical networks
- H04W84/14—WLL [Wireless Local Loop]; RLL [Radio Local Loop]
Landscapes
- Engineering & Computer Science (AREA)
- Computer Security & Cryptography (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
- Transceivers (AREA)
Abstract
A point-to-multipoint radio system comprises a plurality of subscriber units, a beacon transmitter comprising a frequency reference, a modulator and a radio transmitter operable to transmit a radio frequency beacon signal for reception by the plurality of subscriber units, the frequency of the beacon signal being derived from the frequency reference and the modulator being arranged to modulate the beacon signal according to a predetermined modulation scheme, and a hub including a hub transceiver operable to receive radio signals from the subscriber units and to transmit radio signals to the subscriber units. Each subscriber unit including a subscriber transceiver arranged to receive the beacon signal and using the beacon signal, to generate a radio signal to be transmitted to the hub and to correct frequency errors in a radio signal received from the hub.
Description
INCOHERENT BEACONS TO PROVIDE A SPECTRALLY EFFICIENT FREQUENCY REFERENCE IN POINT TO MULTIPOINT RADIO SYSTEMS
This invention relates to the use of an incoherent beacon generated and transmitted from the hub of a Point to Multipoint radio communications system and the specialised receivers required to receive them. The beacon can be received in all the subscriber equipment working with the hub and used as a reference for all their internal oscillators.
Point to Multipoint radio systems are being used increasingly. Examples include mobile telephone networks, rural telephones and microwave video distribution.
These systems comprise one or more hub stations to which a number of subscribers communicate. A new generation of point to multipoint systems is also being introduced to provide high speed internet, business data and closed user group communications.
The Modems used to connect internet subscribers have generally been designed for cable and fibre systems which have different characteristics to radio. Because of this, there are incompatibilities when they are used with radio. Several so-called
Wireless Modems have been introduced in order to simplify the problems.
The disadvantage of using a special Modem is that it is more expensive, primarily because it is non-standard, which in turn means that the complete subscriber equipment will be more expensive. This is a major factor in wideband internet applications, especially because domestic households represent the bulk of the customers, which is a particularly price conscious market.
There would be a major benefit if radio could interface directly to standard internet
Modems without any changes whatsoever to the latter. The major restriction in being able to do this is the particularly stringent frequency accuracy requirements.
All data transmission is allocated into channels. The control software within the system allocates each subscriber to an upstream and to a downstream channel for data to and from the hub respectively. Relatively low frequencies in the order of a few hundred MHz are used in fibre systems and thus the total permissible channel error of +/-20 kHz is readily attainable.
However the lower frequencies are not available to radio systems because other services invariably occupy that part of the spectrum. Only much higher frequencies from 3 to 40 GHz are generally available. Crystals provide the conventional method of establishing frequency references. These have accuracies of +/-10 kHz/GHz over temperature and time which is insufficient to meet the requirement. Thus specialised and therefore expensive techniques such as ovenised crystals have to be used.
One solution to this problem is to establish a reference frequency at the hub and to transmit it to all the subscribers. This so-called beacon then provides a common reference.
As an example, if the signal at the hub is at a frequency f1 and is to be transmitted in a radio system at a frequency of f2, a beacon at (f2-f1) could be used. In this way the transmission frequency is obtained by adding the beacon signal to the signal frequency in a conventional mixer. Then at the receiver, the beacon can be subtracted from the received signal to reproduce the signal back to f1. In this example transmission can be provided without any end-to-end frequency error, even if there is some error in the beacon.
Although this illustrates the principle, in practice such a simple system could not be used because there would almost certainly be restrictions on the beacon transmission frequency. If the beacon has to be transmitted within the same band as the signal, more complex conversion processes are necessary in the hub and/or subscriber. It also means that perfect cancellation of any error in the beacon cannot necessarily be achieved. Thus the principle of using a common precise reference applies.
The use of a single beacon to provide a frequency or phase reference is well established in a number of data, video and telemetry applications. The concept works well when there is only one such beacon in the detection range. However difficulties occur if several hubs, each generating a beacon, exist in the environment.
In this case, the beacon signals may interfere with each other.
Such interference may happen in Point to Multipoint systems if several overlapping hubs are employed to provide continuous coverage in a city, or when a hub comprises a number of transmitters with overlapping coverage from different sectors. Figure 1 illustrates these conditions. In the case where overlapping sectors are used to provide 360 degree azimuth coverage, nulling of the beacon signal can occur over 20% of the area when the signals from one sector are of comparable amplitude to that of the adjacent sector.
The problem could be overcome by each hub, or hub sector, using a different beacon frequency. There are however two disadvantages with this. Firstly it uses more spectrum. Secondly, it means that different categories of subscriber equipment are required to work into different hubs. This involves more complex installation or greater logistics costs to Operators.
According to a first aspect of the invention, there is provided a point-to-multipoint radio system comprising a plurality of subscriber units, a beacon transmitter comprising a frequency reference, a modulator and a radio transmitter operable to transmit a radio frequency beacon signal for reception by the plurality of subscriber units, the frequency of the beacon signal being derived from the frequency reference and the modulator being arranged to modulate the beacon signal according to a predetermined modulation scheme, and a hub including a hub transceiver operable to receive radio signals from the subscriber units and to transmit radio signals to the subscriber units, each subscriber unit including a subscriber transceiver arranged to receive the beacon signal and using the beacon signal, to generate a radio signal to be transmitted to the hub and to correct frequency errors in a radio signal received from the hub.
In this way bi-directional data transmission can take place between the hub and the subscriber units at very precise frequencies. The particular benefit of the beacon is that it enables low cost components to be used in the subscriber equipment because precise frequencies do not have to be generated within each subscriber unit.
When the system is installed, the important feature is to introduce incoherence between all the beacon signals which can be transmitted in the same area thereby to avoid mutual interference between them.
The incoherence can take the form of different amplitude, frequency or phase modulations including small frequency offsets within a band that is sufficiently narrow so as to maintain the accuracy of the data transmission.
This allows the same beacon frequency to be re-used in a multisector hub or in several hubs installed in the same vicinity. In this way, all subscriber units can be identical and the radio spectrum is not wasted by transmitting beacon signals on different frequencies from each hub.
According to a second aspect of the invention there is provided a beacon transmitter for a point-to-multipoint radio system comprising a frequency reference, a modulator and a radio transmitter operable to transmit a radio frequency beacon signal for reception by a subscriber unit, the frequency being derived from the frequency reference and modulated according to a selectable and predetermined modulation scheme.
According to a third aspect of the invention there is provided a subscriber unit for a point-to-multipoint radio system comprising a subscriber transceiver arranged to receive a modulated radio frequency beacon signal and using the beacon signal, to generate a radio signal to be transmitted to a hub and to correct frequency errors in a radio signal received from a hub.
According to a fourth aspect of the invention there is provided a hub for a point-tomultipoint radio system comprising a hub transceiver arranged to receive radio
signals from a subscriber unit and to transmit radio signals to a subscriber unit, the hub transceiver being further arranged to receive a modulated beacon signal and to correct the frequency and/or phase of signals transmitted by the hub transceiver and/or received by the hub transceiver using the beacon signal.
According to a fifth aspect of the invention there is provided a method of providing a frequency reference in a point-to-multipoint radio system having a hub and a plurality of subscriber units, the method comprising the steps of transmitting a modulated beacon signal, generating a hub signal in the hub, transmitting the hub signal to a subscriber unit, receiving the hub signal at the subscriber unit, receiving the beacon signal at the subscriber unit, correcting frequency errors in a frequency source local to the subscriber unit using the beacon signal, and processing the hub signal in the subscriber unit using the corrected local frequency source.
According to a sixth aspect of the invention there is provided a method of providing frequency and/or phase references in a point-to-multipoint radio system having a hub and a plurality of subscriber units, the method comprising the steps of transmitting a modulated beacon signal, receiving the beacon signal at a subscriber unit, correcting frequency errors in a frequency source local to the subscriber unit using the beacon signal, generating a subscriber signal in the subscriber unit using the corrected local frequency source, transmitting the subscriber signal to the hub, and receiving the subscriber radio signal at the hub.
According to a further aspect, the invention also provides apparatus for deriving a frequency reference from a beacon signal comprising an antenna input arranged to receive a radio frequency signal containing a beacon signal whose frequency is generated using a relatively high stability reference oscillator, a relatively low stability reference oscillator, a first oscillator having an oscillation frequency which is related to the oscillation frequency of the reference oscillator, a first down converter arranged to receive a signal from the antenna input and to reduce its frequency by a amount dependent on the oscillation frequency of the first oscillator, a second oscillator having an oscillation frequency which is related to the oscillation frequency
of the reference oscillator in a second variable and controllable ratio, a second down converter arranged to receive the output of the first down converter and to change its frequency by a ratio dependent on the oscillation frequency of the second oscillator, and a controller arranged to receive the output of the second down converter, the controller being operable to cause the second oscillator to sweep its oscillation frequency and to process the output signal of the second down converter to detect a beacon signal in the said output signal, the controller further being operable to adjust the oscillation frequency of the relatively low stability oscillator.
The invention will now be described by way of example with reference to the drawings in which:
Figure 1 is a schematic representation of coverage overlap in a hub transmitting in four 90 degree sectors ;
Figure 2 is a schematic block diagram of a subscriber unit in accordance with the invention; and
Figure 3 is a schematic diagram of a point-to-multipoint radio system in accordance with the invention.
With reference to Figure 3, a point-to-multipoint radio system comprises a hub 30 connected via a radio transmitter 32 to a plurality of subscriber units 34-1,34-2, 34-3 and 34-4.
The hub 30 includes an accurate frequency reference such as a temperature controlled crystal oscillator 36 and a modulator 38 which provides a modulated beacon for transmission to the subscriber units 34. The hub 30 also includes hub control and data generation/receipt unit 40 which provides data encoding and generates control signals for transmission to the subscriber units 34 and which receives data from the subscriber units 34. The hub control and data unit 40 communicates with a data connection 42 into the hub 30. The data connection 42
may for example be a connection into the Internet so that the hub 30 is operable to transmit and receive data over the Internet which has been received and transmitted respectively by the subscriber units 34.
As described in detail below, the incoherent/modulated beacon signal is used by the subscriber units to obtain an accurate frequency reference without the need for expensive and stable local frequency references to be provided in each subscriber unit.
In practical terms, the extent of the modulation and/or frequency offsets of the beacon signal should not be so large that it degrades the accuracy of the system or uses a large part of the spectrum which could otherwise be used to transmit data.
Against this, it should be sufficient to allow the signals from two or more beacons to be received at near full strength at least for a short period of time. An extreme case of amplitude modulation is where all the beacons switch on and off at a pseudo random state such that there is a high probability that only one is received over a predetermined sampling period.
The fact that the beacon signal is not a simple carrier implies that it is difficult for the subscriber to use it as a reference in a simple phase lock synthesiser. The presence of other nearby signals, possibly even data from the same hub also makes this approach difficult to implement.
For these reasons, a dedicated beacon receive circuit needs to be employed to detect the signal and to distinguish it from other emissions that may be received in the subscriber equipment. This circuit can take many different implementation forms but whatever the design, they must be able to distinguish the wanted signal from lower level signals and from data and noise that may also exist in the environment.
A software based scanning receiver meets these requirements by having the ability to scan across the band of interest and to identify the beacon positively in a cluttered environment.
The implementation of the modulated beacon principle is illustrated in Figure 2 which shows the key features of a subscriber radio interfacing to a standard Cable Modem using the DOCSIS standard. In this particular case the transmission frequencies are centred on the bands 10.56 and 10.21 GHz for the up and down streams respectively. However the principle applies to other frequency bands and to other
Modem standards.
A signal is received from a hub via an antenna and low noise amplifier (LNA) 2. It is then down-converted 3 using a first stage oscillator 4 which is locked to a crystal reference oscillator 6 by a frequency divider and synthesiser circuit 8.
The output from the first down converter 3 is split. The data is filtered 10 and fed via a diplexer 12 to a cable modem (not shown). The other part of the output from the first down converter 3 is fed to a second down converter 14 which is fed from a second stage oscillator 16, also locked to the crystal reference 6 by a synthesiser circuit 24. This oscillator 16 is driven from a dedicated controller 18 which also receives the filtered and detected output 20 and 22 from the second stage down converter 14.
The controller 18 commands the synthesiser 24 to move the second stage oscillator 16 in a scan across a predetermined frequency band in order that all the signals adjacent to the expected beacon signal frequency can be detected. Some signals could be data, others could be simple carriers. In both cases they can be distinguished from the modulated beacon by suitable software processing in the controller 18. Similarly, low level signals with similar spectrums to the beacon can be rejected.
In this way the beacon signal can be identified, its level measured and the frequency error in the crystal reference oscillator 6 calculated.
The second stage oscillator 16 is now set back to its nominal frequency. Using the calculated frequency error, the controller 18 adjusts the control voltage of the crystal reference oscillator 6-The resultant change of the output frequency of the crystal reference oscillator 6 will cause the frequency of the first stage oscillator 4 to
change, which in turn will cause the frequency of the down converted beacon signal to change. The controller 18 measures the detected signal strength from detector 22 to establish if it has moved the crystal reference oscillator 6 to the point where the beacon is in the passband of filter 20.
This iterative process continues until the crystal reference oscillator 6 is set to the control voltage which causes the beacon to be within the filter 20 passband. At this point the beacon has been found and the error in the crystal reference oscillator 6 removed. Since all the oscillators within the subscriber unit use this reference then they must all now be within tolerance of the correct frequency. The second stage oscillator 16 continues to be stepped up and down to allow the system to find and remove any errors in the crystal reference oscillator 6 that may occur as it warms up or if the ambient conditions change.
If the beacon is lost for any reason, the system reverts to the acquisition sequence as used when the equipment is initially powered.
In this illustration, it is clearly necessary to ensure that the filter characteristic of the filter 20 is sufficiently well defined to provide the required system accuracy. Also, the initial accuracy of the crystal reference oscillator 6 has to be compatible with the sweep range of the system as it performs acquisition.
The above approach illustrates one possible implementation. It will be appreciated by the skilled artisan that other configurations are possible in which the principle of an incoherent/modulated beacon can usefully be exploited.
Claims (10)
1. A point-to-multipoint radio system comprising : (a) a plurality of subscriber units, (b) a beacon transmitter comprising a frequency reference, a modulator and a radio transmitter operable to transmit a radio frequency beacon signal for reception by the plurality of subscriber units, the frequency of the beacon signal being derived from the frequency reference and the modulator being arranged to modulate the beacon signal according to a predetermined modulation scheme, and (c) a hub including a hub transceiver operable to receive radio signals from the subscriber units and to transmit radio signals to the subscriber units, each subscriber unit including a subscriber transceiver arranged to receive the beacon signal and using the beacon signal, to generate a radio signal to be transmitted to the hub and/or to correct frequency errors in a radio signal received from the hub.
2. A system according to claim 1, wherein the hub receives the beacon signal from the beacon transmitter and wherein the frequency of signals transmitted by the hub transceiver and/or received by the hub transceiver is corrected using the beacon signal.
3. A system according to claim 1 or claim 2, wherein the beacon transmitter is an integral part of the hub.
4. A system according to any preceding claim, including a plurality of beacon transmitters forming a set of beacon transmitters having mutually overlapping coverage and wherein the modulator of each beacon transmitter in the set is arranged to use uncorrelated modulation or small frequency offsets in the same frequency spectrum as that of the other beacon transmitters in the set, whereby interference between the beacon signals is mitigated.
5. A beacon transmitter for a point-to-multipoint radio system comprising a frequency reference, a modulator and a radio transmitter operable to transmit a radio frequency beacon signal for reception by a subscriber unit, the frequency being derived from the frequency reference and modulated according to a selectable and predetermined modulation scheme.
6. A subscriber unit for a point-to-multipoint radio system comprising a subscriber transceiver arranged to receive a modulated radio frequency beacon signal and using the beacon signal, to generate a radio signal to be transmitted to a hub and/or to correct frequency errors in a radio signal received from a hub.
7. A hub for a point-to-multipoint radio system comprising a hub transceiver arranged to receive radio signals from a subscriber unit and to transmit radio signals to a subscriber unit, the hub transceiver being further arranged to receive a modulated beacon signal and to correct the frequency and/or phase of signals transmitted by the hub transceiver and/or received by the hub transceiver using the beacon signal.
8. A method of providing a frequency reference in a point-to-multipoint radio system having a hub and a plurality of subscriber units, the method comprising the steps of: (a) transmitting a modulated beacon signal, (b) generating a hub signal in the hub, (c) transmitting the hub signal to a subscriber unit, (d) receiving the hub signal at the subscriber unit, (e) receiving the beacon signal at the subscriber unit, (f) correcting frequency errors in a frequency source local to the subscriber unit using the beacon signal, and (g) processing the hub signal in the subscriber unit using the corrected local frequency source.
9. A method of providing a frequency reference in a point-to-multipoint radio system having a hub and a plurality of subscriber units, the method comprising the steps of:
(a) transmitting a modulated beacon signal, (b) receiving the beacon signal at a subscriber unit, (c) correcting frequency errors in a frequency source local to the subscriber unit using the beacon signal, (d) generating a subscriber signal in the subscriber unit using the corrected local frequency source, (e) transmitting the subscriber signal to the hub, and (f) receiving the subscriber radio signal at the hub.
10. Apparatus for deriving a frequency reference from a beacon signal comprising: (a) an antenna input arranged to receive a radio frequency signal containing a beacon signal whose frequency is generated using a relatively high stability reference oscillator, (b) a relatively low stability reference oscillator, (c) a first oscillator having an oscillation frequency which is related to the oscillation frequency of the reference oscillator, (d) a first down converter arranged to receive a signal from the antenna input and to reduce its frequency by an amount dependent on the oscillation frequency of the first oscillator, (e) a second oscillator having an oscillation frequency which is related to the oscillation frequency of the reference oscillator in a second variable and controllable ratio, (f) a second down converter arranged to receive the output of the first down converter and to change its frequency by an amount dependent on the oscillation frequency of the second oscillator, and (g) a controller arranged to receive the output of the second down converter, the controller being operable to cause the second oscillator to sweep its oscillation frequency and to process the output signal of the second down converter to detect a beacon signal in the said output signal, the controller further being operable to adjust the oscillation frequency of the relatively low stability oscillator.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0023484A GB2367215A (en) | 2000-09-25 | 2000-09-25 | In a point to multipoint system establishing a reference frequency at the hub and transmitting it to all subscribers as a common reference |
| PCT/GB2001/004110 WO2002025966A1 (en) | 2000-09-25 | 2001-09-14 | Incoherent beacons to provide a spectrally efficient frequency reference in point to multipoint radio systems |
| AU2001286105A AU2001286105A1 (en) | 2000-09-25 | 2001-09-14 | Incoherent beacons to provide a spectrally efficient frequency reference in point to multipoint radio systems |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0023484A GB2367215A (en) | 2000-09-25 | 2000-09-25 | In a point to multipoint system establishing a reference frequency at the hub and transmitting it to all subscribers as a common reference |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0023484D0 GB0023484D0 (en) | 2000-11-08 |
| GB2367215A true GB2367215A (en) | 2002-03-27 |
Family
ID=9900091
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0023484A Withdrawn GB2367215A (en) | 2000-09-25 | 2000-09-25 | In a point to multipoint system establishing a reference frequency at the hub and transmitting it to all subscribers as a common reference |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU2001286105A1 (en) |
| GB (1) | GB2367215A (en) |
| WO (1) | WO2002025966A1 (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4455650A (en) * | 1979-10-24 | 1984-06-19 | Gendrot Andre Jean C | System of beacons for the transmission of information |
| EP0779756A2 (en) * | 1995-12-15 | 1997-06-18 | AT&T Corp. | Apparatus and method for transmitting a signal |
| EP0928084A2 (en) * | 1998-01-02 | 1999-07-07 | Mitsubishi Denki Kabushiki Kaisha | Universal modem for digital video, audio and data communications |
| US6028853A (en) * | 1996-06-07 | 2000-02-22 | Telefonaktiebolaget Lm Ericsson | Method and arrangement for radio communication |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8305037D0 (en) * | 1983-02-23 | 1983-03-30 | Mcmichael Ltd | Radio communications systems |
| US5410588A (en) * | 1991-04-03 | 1995-04-25 | Kabushiki Kaisha Toshiba | Mobile radio communications system having a supervising radio transmitting station for transmitting a reference synchronizing signal to a first and second base stations via a radio link |
| US6212397B1 (en) * | 1996-12-23 | 2001-04-03 | Texas Instruments Incorporated | Method and system for controlling remote multipoint stations |
| EP0949770A1 (en) * | 1998-04-09 | 1999-10-13 | BetaResearch Gesellschaft für Entwicklung und Vermarktung digitaler Infrastrukturen mbH | Bidirectional broadcasting system |
-
2000
- 2000-09-25 GB GB0023484A patent/GB2367215A/en not_active Withdrawn
-
2001
- 2001-09-14 WO PCT/GB2001/004110 patent/WO2002025966A1/en active Application Filing
- 2001-09-14 AU AU2001286105A patent/AU2001286105A1/en not_active Abandoned
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4455650A (en) * | 1979-10-24 | 1984-06-19 | Gendrot Andre Jean C | System of beacons for the transmission of information |
| EP0779756A2 (en) * | 1995-12-15 | 1997-06-18 | AT&T Corp. | Apparatus and method for transmitting a signal |
| US6028853A (en) * | 1996-06-07 | 2000-02-22 | Telefonaktiebolaget Lm Ericsson | Method and arrangement for radio communication |
| EP0928084A2 (en) * | 1998-01-02 | 1999-07-07 | Mitsubishi Denki Kabushiki Kaisha | Universal modem for digital video, audio and data communications |
Non-Patent Citations (2)
| Title |
|---|
| www.galleon.eu.com * |
| www.microsoft.com * |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2002025966A1 (en) | 2002-03-28 |
| AU2001286105A1 (en) | 2002-04-02 |
| GB0023484D0 (en) | 2000-11-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |