Abstract:
A method for distributing radio band signals between stations in a broadband structure. Radio band signals transmitted from a first station are converted to intermediate signals for transfer through a wire connection while maintaining code structure and modulation of the radio signals. The intermediate signals transferred over the wire connection are received and converted to radio band signals while maintaining code structure and modulation of the radio signals. A system and a method for transmitting radio signals in a broadband structure including a first network, said first network operating on air as a first medium. Said first network is connected to a second network through a first media converting means for converting the radio signals for transfer through the second network, said second network operating on wire as a second medium. The second network is connected to a third network through at least a second media converting means, said third network operating on a medium different from the second medium. The media converting means are designed to maintain code structure and modulation of the radio signals and stations of the first network are operatively connected to stations of the third network.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a system for transmitting data signals in a broadband structure. The system can be used for services built on the internet protocol (IP) and for providing access to end users. 
       PRIOR ART 
       [0002]    Prior art systems normally use cable TV networks (Docis standards), xDSL in public telephone networks or cable, such as CAT (CAT 5, 6 or 7). In cable TV networks there are limitations with regard to bandwidth restrictions and bandwidth use for downlink and/or uplink. Amplifiers and other devices also limit the use of such networks i.e. head end containing D1, D2 and D3 to end users. In these systems some kind of wire is used as a transfer medium. In apartment houses (on D3 level) there is typically no need for amplification in either direction. 
         [0003]    Transmission of modulated information through copper wires in local public telephone networks is limited by for instance the distance between a telephone station and terminals or end users. Also the selected transmission speed and possible other users on the same cable branch limit such a transmission as a result of physical properties, such as bandwidth, noise, crosstalk and interference of the cables. These limitations result in undesired restrictions in the transfer of streaming IP flows in services such as high definition TV and video on demand. The limitations also constitute a drawback when new services are developed. 
         [0004]    Generally in wired and wireless communication systems different types of modulation of carriers are used together with signal processing. Wireless transmission using the air as a transfer medium is highly limited by air attenuation, physical obstructions such as walls and floors. Well-chosen frequencies improve the situation. Also a higher transmit power can be used but this is a drawback when there is an intention to restrict contamination by electromagnetic radiation. 
         [0005]    More and more services are made available requiring even higher bandwidths and bit transfer rates that cannot be provided easily and efficiently with existing techniques. There is a further need also for higher bit rates in both directions to support active end users. In this respect is has been considered too expensive and time consuming to install fibres or cables that can provide high capacity services in existing buildings, sub-urban and city areas. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to overcome drawbacks mentioned above and to provide a system that will allow a more efficiently usage of existing wired and wireless networks and communications solutions based on wireless standards for fixed and/or nomadic and/or mobile services. In accordance with the invention it will be possible also to transparently transmit digital signals between stations through any wire and/air medium and/or a combined wired and wireless network including in the latter case at least one exchange of medium, such as cable to air or air to cable. The digital signals can be transmitted in both directions between terminals. Fixed broadband access as well as public broadband access indoors as well as outdoors are included. 
         [0007]    In accordance with the invention signals that are transmitted in a first communication system based on a first medium are received and converted in a first media converting means. After the conversion the signals are transmitted in a second communication system based a second medium. The converted signals are then converted in a second step in a second media converting means for further transmission in a different medium. The different medium can be equal to the first medium. 
         [0008]    Each of the stations uses digital modems in which base bands are converted to suitable analogue carrier/carriers at selected frequency bands so as to transfer data over different media, such as air or any type of cable, depending on standards of available networks. Different systems can be isolated by filtering techniques and/or by, selection of appropriate frequencies. It is possible also to adapt impedance, signal level and/or frequency band to allow the transfer of data through the wires. Also radio standards based on time division duplex and/or frequency division duplex and/or half frequency division duplex can be used when data are transferred through the wires. 
         [0009]    When wires are used for the communication the frequency of a carrier or carriers transmission (strictly speaking a radio channel) is selected to avoid interference with other stations and/or other applications that use the same medium in parallel. However, the frequency is selected taking the physical properties of the wire and the subscriber&#39;s terminals into consideration. 
         [0010]    In one embodiment in accordance with the invention a first medium is air, the second medium is a coaxial cable and the different medium again is air. Another embodiment in accordance with the invention allows that the second medium consisting of a cable system is the only medium to be used. In such case wireless stations communicate with each other via coaxial and/or telecom and or data cable network systems via medium conversion where radio signals are adjusted to an appropriate carrying frequency band for the used medium and or to a selected frequency that include avoidance with other possible co-located signals like standards cable-tv-services, etc. which are applied on the same network system. 
         [0011]    In other embodiments other medium and or medium conversions are used in various combinations between a first and a second etc. to arrange transparent transfer of carriers via analogue pipes arranged for wireless stations in communications. In accordance with the invention it is possible to repeat the media conversions steps in a non-limited way as may be required in each specific application. 
         [0012]    By using a wired network or a wired network as part of a combined network it is possible to overcome restrictions and limitations of a first medium via air by wireless stations specifically in dense user environment, due to signal degradation through air, in walls, ceilings and roofs and other obstacles. Signals from wireless stations using an existing cable medium for example to establish communication within a building to overcome obstacles are converted via the medium converter to suit the specific cable medium to reach another station which in its turn is connected to a corresponding station connected to a similar medium converter. 
         [0013]    Signals from stations in the wireless communication network that are received and or transmitted are converted to suit a second medium, such as coaxial cable, copper wires or fibre cables, and then transferred through the second medium to stations that utilize the second medium. During conversion the code structure and modulation of the original signal are maintained. 
         [0014]    The invention can be implemented in existing wireless standards or using such standards such as IEEE 802.11x, IEEE 802.16x, IEEE 802.15x, other IEEE standards including UMTS not excluding DOCIS. Additionally other de-facto wireless standards evolving standards or solutions that are arranged to establish communications between stations via modulated carriers through air or wires or in combination are included. Different topologies for communication between stations include point-to-point, point-to-multipoint and multipoint-to-multipoint. 
         [0015]    Any existing wired technology can be included as a medium in accordance with the invention. Examples of such technologies are cable-TV, telephone communication, computer networks and electrical power distribution. The physical implementations include coaxial cable, twin wires for telephone communication, copper wires for data transmission and/or telephone communication and/or fibre cables i.e. for all types of data transmission having a spectrum available that enables transparent carrying of modulated carriers on suitable frequency bands. 
         [0016]    Wireless access to a network or the internet can be provided inside or close to a building where an installation in accordance with the invention is implemented. Means arranged outside the building connects a WLAN, WiMAX and UMTS or similar system to a wired network part of the installation inside the building. 
         [0017]    On the reverse means arranged inside the building including arrangements of access points in a basement or similar location to access apartments via coaxial cable overlaid on cable TV standards. Additionally these access points can also be used to reach access feasibilities outside the building. Such cable arrangements indoor include star/branch and tree structures. 
         [0018]    The communication between the stations includes a transparent transmission of digital information. Antenna applications and stations involved will not be aware of the change of media during the transmission. End users at the stations using different medias and communication techniques will not be aware of the change of media during the transfer of information. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention will now be described in more detail with reference to embodiments thereof shown in the accompanying drawings. 
           [0020]      FIG. 1  is a schematic view showing a first embodiment of the invention. 
           [0021]      FIG. 2  is a schematic view showing a second embodiment of the invention. 
           [0022]      FIG. 3  is a schematic block diagram of a media converting means included in the embodiment shown in  FIG. 1 . 
           [0023]      FIG. 4  is a diagram showing schematically the attenuation of a cable in a TV cable network. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    In the embodiment shown in  FIG. 1  a wireless first network  10  includes a plurality of first stations  11  and a combined gateway and wireless access point  12  providing the first network  10  with services such as access to the internet  13 . The stations  11  communicate with each other and with the gateway  12  through air  14  as a first transfer medium. Radio signals are broadcasted between the access point  12  and the first stations  11 . 
         [0025]    A wired second network  15  is provided in a building or site that can include a plurality of buildings. The second network  15  includes a plurality of second stations  16  connected through a wire  17  forming a second medium. In the shown embodiment the second network is a conventional cable network in a building including a coaxial cable and/or a telecom and/or data cable. The cable network receives digital video signals from a satellite receiver  18  that can be located distant from the building. A dashed line  37  indicates that the cable network also can be connected to the internet to provide internet access to the second stations  16 . 
         [0026]    A connecting box  19  is arranged for instance in a basement or other suitable location in the building for distributing the video signals in the cable network. The stations of the second network include a set top box or similar device that can be connected to a TV set considering cable TV network applications or telephone networks for telecom cables or data cables for data applications. The set top box is connected to a TV outlet or corresponding terminal of the cable network. 
         [0027]    In accordance with the invention a first media converter  20  is connected to a first receiving and transmitting means  21 , such as an antenna or antenna systems in for instance a MIMO system, that is arranged to communicate with the wireless first network  10 . The first media converter  20  is also connected to the wired second network  15 . In the shown embodiment the connection is made at the connecting box  19 . Signals broadcasted in the wireless first network  10  are received in the receiving and transmitting means  21  and forwarded through the wired second network  15  after being converted in the first media converter  20 . The conversion of the signal in the first media converter  20  does not include any change of coding or modulation of the radio signal. An embodiment of the media converter is described below with reference to  FIG. 3 . 
         [0028]    A second media converter  22  is connected to the second network  15  and detects signals originating from the wireless first network  10  and being transferred through the second medium at a frequency scheme that do not interfere with the frequency scheme used by the cable network. These detected signals are converted in the converter  22  and transmitted to the air through a second receiving and transmitting means  23 . Air is now the transfer media again. Again the conversion of the signal in the media converter does not include any change of coding or modulation of the original signal. 
         [0029]    A plurality of third stations  24  communicates through air with each other and with the first stations  11  through the second receiving and transmitting means  23  and the second network  15 . Signals originating from the wireless first network  10  can be received by the third stations  24  as if they were physically located in the vicinity of the first stations  11 . The communication between the first stations  11  and the third stations takes place in both directions. It is possible also for the first stations  11  as well as the third stations  24  to access the internet  13 . 
         [0030]    A network management control and supervision centre  50  is connected to the internet  13  and is able to reach the multiple stations  11 ,  24 , first receiving and transmitting means  21  and second receiving and transmitting means  23  via IP networking protocols or similar. 
         [0031]    An alternative embodiment in accordance with the invention is shown in  FIG. 2 . Here a conventional cable network  25  is connected to a satellite receiver  18  through a connecting box  19  in a way similar to the embodiment shown in  FIG. 1 . A plurality of end users  29  are connected to the cable network  25  in one or multiple buildings or sites  30 . Each end user has a set top box or similar device allowing him to connect a TV set to the cable network. 
         [0032]    A coaxial cable network of standard type normally operates on a bandwidth up to 860 MHz for standard cable TV services even though most systems physically are capable of operating at considerably higher frequencies. The capacity at bands within cable or outside cable TV standards and higher frequency bands is utilized in accordance with the invention as will be described below as an example. 
         [0033]    A connection  26 , such as a logical gateway, to the internet  13  or another service is connected to a first receiving and transmitting means  27 , such as an antenna or an antenna combined with a station, located inside or outside the building  30  from where it may communicate with other receiving and transmitting means through air and/or cable. The gateway  26  and the receiving and transmitting means  27  form an access point in a wireless network. Multiple access points of this type can be provided in accordance with the invention. Signals are transmitted to stations that are provided with hardware and software for wireless communication, such as IEEE 802.11x WLAN standards. Due to signal attenuation within the building the service range through air is very limited. Users located within the building but at some distances from the access point will normally not be able to access the internet or other services through this route at an acceptable speed. 
         [0034]    In accordance with the invention a first media converter  28  is connected to the gateway  26  at the same functional level as the first receiving and transmitting means  27 , that is at a radio frequency level and/or intermediate frequency level. In the first media converter  28  signals at the radio frequency level to and from the first receiving and transmitting means  27  are converted to be suitable for transmission in the cable network transparently. The first media converter  28  is connected to the cable network through a mixer  31  that will allow signals to and from the gateway  26  to be transferred over the cable network without interfering with the cable TV services. 
         [0035]    A second media converter  32  is provided at the location of an end user  29  and is connected to the cable network  25 . The second media converter  32  is functionally similar or identical to the first media converter  28 . Also at the location of the end user  29  there is provided a second receiving and transmitting means  33  similar or identical to the first receiving and transmitting means  27 . The second media converter  32  and the second receiving and transmitting means  33  form a micro cell that will allow user access to services that are available through the gateway  26 . The micro cell in a building or a macro cell to reach out of the building which can be based on for instance WLAN, Wi-Fi, WiMax or UMTS. 
         [0036]    In accordance with the invention the second receiving and transmitting means  33  will function as an extension of the first receiving and transmitting means  27 . Computers and other equipment that are located not too distant away from the second receiving and transmitting means  33  and that are provided with means for a wireless connection will have access to the internet  13  and/or other types of networks through the cable network  25 . 
         [0037]    Each end user  29  can be located in separate premises  35  in the building  30  and will have full access from a computer  34  such as a laptop through the gateway  26  as if the end user was located in the vicinity of the first receiving and transmitting means  27 . This applies also when the computer  34  is connected to the second receiving and transmitting means  33  through a separate cable  38 . 
         [0038]    Since the communication to and from the end user includes a wireless connection there will be a “leakage” of the service provided by the gateway  26  from the premises of the end user to other parties located in the vicinity of the second receiving and transmitting means  33 , such as an external computer  36 . This “leakage” can be utilized by arranging functions and means to allow other users to subscribe to internet access services. Such functions and means can include authorization, authentication and security arrangements. 
         [0039]      FIG. 2  also illustrates schematically an interconnection or cable  38  between the second media converter  32  and the computer  34 . This interconnection can include a connection carrying an rf signal if a corresponding wireless station is built into the computer  34  and or a standard digital interface for a normal digital interconnection such as RJ45, Firewire, USB etc. 
         [0040]    One embodiment of a media converter, such as the first media converter  20 , is shown in  FIG. 3 . The media converter is connected to a first receiving and transmitting means  21 , such as an antenna or an antenna system for providing a wireless communication with a first station  11  being part of a wireless first network. The wireless communication between the first station and the receiving and transmitting means  21  can be based on Time Division Duplex (TDD) and/or Frequency Division Duplex (FDD) and/or half Frequency Division Duplex. 
         [0041]    The media converter  20  is connected to a wired second network  17  including a plurality of second stations  16 .  FIG. 3  also shows a combination where a TDD station is arranged for half duplex (HFDD). When a station is based on TDD it is connected to a first circulator  39 . Signals aimed for a third station  24  is passed through a mixer  40 , which is fed by an oscillator  41 , and further on to a second circulator  42 . In the mixer  40  the frequency of the signal can be changed to a frequency that is appropriate for further transmission in the second network  17  for instance so as to avoid interference with other signals appearing on the cable and/or to match transfer characteristics of said second network. 
         [0042]    An amplifier (not shown) can be included in the mixer  40  or provided between the mixer  40  and the second circulator  42 . In a similar way a filter (not shown) normally is provided in or in combination with the mixer  40  or arranged between the mixer  40  and the second circulator  42 . The second circulator  42  is connected to an impedance adapter  43 , which is used adapt the impedance to an appropriate value for transferring the signal to the second network  17 . In a FDD or TDD to half FDD application output means  44  and input means  45 , respectively, are used to transfer signals from and to the media converter  20 . 
         [0043]    A controlling or supervising functional unit  48  is connected meant to the medium converters,  20  and or  22  via a digital interface  49  via receiving and transmitting means  21 ,  23  respectively and or any other station and or via a IP network and management centre. 
         [0044]    A second media converter  22  is connected in a similar way to the wire  17 . The second media converter  22  comprises similar or identical means as compared to the first media converter  20 . It is apparent from  FIG. 3  that the second media converter  22  operates the same way as the first media converter  20  and no further description is necessary in this respect. 
         [0045]    In more complex applications a plurality of systems in accordance with the invention is used in combination. Receiving and transmitting means used by different systems, for example MIMO based systems, can operate at overlapping frequencies when air is the transfer medium for radio signals. After conversion in a plurality of media converters including frequency transformation the frequencies of the different systems can be separated and transferred through a single cable or wire without interference. After transfer through the cable and a conversion and frequency transformation the signals are again transmitted through air, also on overlapping frequencies. 
         [0046]    The attenuation of a cable in a TV cable network schematically is shown in  FIG. 5 . However, approximately the same properties will apply for other systems. The y axis depicts the carrier signal level S and the x axis depicts the frequency f. A frequency value f1 is an approximate upper limit for an existing service  46  of a cable in a cable network. In an application where the cable is a coaxial cable and the service is cable TV f1 is equal to approximately 860 MHz. Frequencies above f1 but below a theoretical upper limit f2 are available for systems utilizing the present invention for 47. 
         [0047]    In practice the available frequency space is limited to a lower frequency f3 by other equipment used in or connected to subscriber&#39;s outlets. A further limitation to a frequency value of f4 is the result of attenuation properties of the outlet, filters and directional couplers. Frequency bands below f1 that are not used by the existing service can be used by the system in accordance with the invention.