Abstract:
A management system for controlling a digital subscriber loop telecommunications network identifies radio frequencies used by wireless transmitters in the vicinity of each electrical connection, and controls transmission frequencies carried over the respective digital subscriber loops to prevent transmission on frequencies in which nearby radio transmitters are operating.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is a National Phase entry of PCT Application No. PCT/GB2010/000013, filed Jan. 7, 2010, which claims priority from European Patent Application No. 09250100.6, filed Jan. 15, 2009, the disclosures of which are hereby incorporated by reference herein in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to telecommunications systems and in particular to the management of network equipment interfacing between a network and individual customer premises systems. Such equipment is widely dispersed geographically, and has to operate without direct human supervision and in a wide variety of environments and circumstances. 
       BACKGROUND ART 
       [0003]    The increasing use of radio-based communications systems can cause significant impairment of the signal in the wired network, as the wires themselves act as antennas, and the resulting RF signals can interfere with transmissions in the system. This is particularly so as the frequencies in use in the wired network rise above the 2.2 MHz currently in use for ADSL2+(Asymmetric digital subscriber Line) to 7.05 MHz for VDSL2 (very high rate digital subscriber loop) and then 30 MHz or even 300 MHz for future proposed DSL systems. 
         [0004]    It is known for notches to be put into the RF spectrum to prevent DSL transmission on bands in which radio transmitters are known or discovered to be operating—see the ITU-T standard G992.5. 
       SUMMARY OF THE INVENTION 
       [0005]    According to an embodiment of the invention, there is provided a dynamic line management system for a digital subscriber loop telecommunications network for carrying data between a remote access server and a plurality of individual network terminations over connections which use electrical connections for at least part of their length, comprising a data collection system for identifying radio frequencies used by wireless transmitters in the vicinity of each electrical connection, and a transmission management system for managing the spectrum of transmission frequencies carried over the respective digital subscriber loops to prevent transmission in frequency ranges in which nearby radio transmitters are operating, 
         [0006]    wherein the data collection system comprises, at each of two or more nodes in the electrical part of the network, data collection apparatus for collection of data relating to the RF environment at the respective nodes, and wherein each such node also comprises a data exchange system to allow data collected locally to each node to be exchanged between the nodes. 
         [0007]    According to another embodiment, there is provided a method of controlling a digital subscriber loop telecommunications network for carrying data between a remote access server and a plurality of individual network terminations over connections which use electrical connections for at least part of their length, comprising the steps of identifying radio frequencies used by wireless transmitters in the vicinity of each electrical connection, and controlling transmission frequencies carried over the respective digital subscriber loops to prevent transmission on frequencies in which nearby radio transmitters are operating, 
         [0008]    wherein data relating to the RF environment is collected at each of two or more nodes in the electrical part of the network, and such data is exchanged between the nodes. 
         [0009]    Thus, if there is a known interferer in the vicinity then the attempted use of the relevant frequencies for incoming traffic can be prevented, by transmitting this information to neighboring remote nodes to update their ‘picture’ of the local RF ‘signature’ for that particular region. 
         [0010]    Embodiments of the invention can be implemented at any level of the distribution system, but are preferably implemented in each local remote node of a Fiber to the Distribution Point system, at the point where the signals switch from the optical domain to the electrical domain and vice versa. Thus each remote node can respond to its own RF environment, reducing the signalling overhead as some of the data it requires is measured locally. 
         [0011]    It would be possible to train an initial artificial neural network such as a Multilayer Perceptron (MLP) to operate a dynamic line management (DLM) system with some default initial values. If the Radio Frequency ingress and egress conditions could be considered prior to the commencement of the training of each local MLP, this would allow rapid convergence to a locally trained MLP at each node. This RF augmentation information could contain the following data:
       local radio &amp; TV broadcast transmitters and estimations of reception powers at the remote node location,   geographical remote node location with regards to typical RF interference experienced at that point,   local sources of repetitive RF interference obtained from the RF section of the MLPs from neighboring remote nodes,   local radio amateur frequencies obtained via post-code information in relation to the remote node location. This may be relevant both to avoid interference on the DSL caused by the local radio amateurs, but also to avoid causing interference to the relatively weak signals which the local radio amateur users are trying to detect.       
 
         [0016]    Embodiments of the invention can be implemented in a module of the DLM system for use in the decision making process, by providing information on how the profiles can be best adapted for the prevailing RF environment. For example a specific “notch” can be applied in the DSL RF spectrum if a local radio amateur is transmitting at that frequency (ingress control) or put a notch in the spectrum if a local radio amateur is attempting to listen at that frequency (egress control). In addition the RF module is able to consider the RF situation at neighboring remote nodes and use this information to augment its local knowledge of the RF environment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Embodiments of the invention will now be discussed, by way of example, with reference to the drawings, in which: 
           [0018]      FIG. 1  depicts a conventional digital subscriber loop system 
           [0019]      FIG. 2  depicts a fiber-to-the-data-point system 
           [0020]      FIG. 3  shows the functional elements that co-operate to implement the invention. 
           [0021]      FIG. 4  shows how a module to perform these functions is integrated into a dynamic line management system implemented in a node of a FttDP system. 
       
    
    
       [0022]    It should be understood that these Figures illustrate the functional elements of the system, which may in practice be embodied in one or more electronic components or in software. 
       DETAILED DESCRIPTION 
       [0023]    As shown in  FIG. 1 , in conventional Digital Subscriber Loop (DSL) services, provided from the exchange  39  (or cabinet), each customer premises  2  has a dedicated physical connection  30  to the DSL access multiplexer (DSLAM)  31  in the exchange  39 . The connections from the exchange  39  to several different customer premises  2  may pass through a single distribution point  1 , but each connection is a complete end-to-end connection. 
         [0024]    A management system  18  can be provided to optimize the service for each customer by maximizing the data rate over the physical layer  30  (subject to a predetermined maximum) while maintaining the stability of the line. This is achieved for each line using a Dynamic Line Management (DLM) system and a Rate Adaptive Management Box (RAMBo)  41  which automatically selects the optimum rate profile for each line. The chosen profile rate (upstream and downstream) supported by the line is also applied to the BRAS (Broadband Remote Access Server)  42  serving the user connection  32  so that the services provided over the DSL line  30  match the physical capabilities of the line. The BRAS is not located at the exchange but is located deeper in the network. It can handle many thousands of lines and would provide the broadband services for many exchanges). 
         [0025]    The physical layer connectivity is provided by a Digital subscriber line access multiplexer (DSLAM) capped at a predetermined rate limit, e.g. SMbit/s, and the BRAS provides the services to the DSLAM so that the services are capped to the same rate limit so that there is rate matching between the physical line and the services that are applied over that line. 
         [0026]      FIG. 2  depicts a fiber-to-the-distribution-point (FttDP) system. In such systems the connections  32  between the optical line terminal  33  in the exchange and the individual distribution points  1  are provided by optical fiber, each carrying the traffic for all the final drop connections  30  served by that distribution point. This allows the distribution point to serve a large number of customer premises. Instead of a single DSLAM  31  providing the line statistics for thousands of lines at one convenient location, there could be a large number of remote nodes  1  (located at the distribution points), each provisioning between 8 and 24 lines. 
         [0027]    Because of the transition between optical fiber and electrical “copper” connections at the distribution points, they have more capabilities than a typical copper-to-copper distribution point. Essentially the modem conventionally located in the DSLAM  31  at the exchange  39  is instead located in a mini-DSLAM  34  at the DP  1  (only shown for one DP in  FIG. 2 ). Thus the DSLAM  31  and BRAS  42  functions are no longer co-located. 
         [0028]      FIG. 3  depicts a RF interference compensating module  14  which is in communication with a dynamic line management system  18 , and is also capable of exchanging data with similar modules  12  associated with the dynamic line management systems of other points in the network. It has means  13  for monitoring the local RF environment. The module  14  includes a store  38  of data relevant to its location, such as its geographical co-ordinates, postal code, or the like. This data may be entered manually or derived from a global positioning sensor or the like. 
         [0029]    The module  14  also includes a query function  36  which interrogates a central database  56  to identify known sources of RF signals in the area identified by the data in the store  38 —for example details of local radio amateur frequencies obtained via post-code information, and details of local radio &amp; TV broadcast transmitters and estimations of reception powers. This is supplemented by data discovered by the module&#39;s own detection system  57  and exchanged with data from neighboring nodes  12 . 
         [0030]    The collected data is collated and stored in a memory, to identify the local RF environment. This information is used to control the RF frequencies used by the dynamic line management system  18 . The data can be updated periodically as local conditions can change. 
         [0031]    The data exchange function  35  also retrieves data from the memory  37  for transmission to the neighboring nodes  12 . 
         [0032]    As shown in  FIG. 1 , in conventional Digital Subscriber Loop (DSL) services, provided from the exchange  39  (or cabinet), each customer premises  2  has a dedicated physical connection  30  to the DSL access multiplexer  31  in the exchange. The connections from the exchange  39  to several different customer premises  2  may pass through a single distribution point  1 , but each connection is a complete end-to-end connection. 
         [0033]    A management system  18  can be provided to optimize the service for each customer by maximizing the data rate over the physical layer  30  (subject to a predetermined maximum) while maintaining the stability of the line. This is achieved for each line using a Dynamic Line Management (DLM) system  40  coupled to a Rate Adaptive Management Box (RAMBo)  41  which automatically selects the optimum rate profile for each line. The chosen profile rate (upstream and downstream) supported by the line is also applied to the BRAS (Broadband Remote Access Server)  42  at the exchange end of the connection  32  so that the services provided over the DSL line  30  match the physical capabilities of the line. 
         [0034]      FIG. 2  illustrates a fiber-to-the-distribution-point (FttDP) system. In such systems the connections  32  between the Digital subscriber line access multiplexer (DSLAM)  31  in the exchange and the individual distribution points  1  are provided by optical fiber, each carrying the traffic for all the final drop connections  30  served by that distribution point. This allows the distribution point to serve a large number of customer premises. 
         [0035]    Because of the transition between optical fiber and electrical “copper” connections at the distribution points, the distribution points have more capabilities than a typical copper-to-copper distribution point. Essentially the modem normally located in the DSLAM at the exchange is instead located in a mini-DSLAM at the DP. Therefore as well as having some active electronics at the DP, some intelligence can be added to make this mini-DSLAM autonomous with regards to setting its own maximum stable DSL rate. This allows the line characteristics to be measured at the distribution points. 
         [0036]    The DSL modem located at the distribution point has the ability to draw statistics both from itself and the equivalent modem on the other end of the local loop located at the customer premises (i.e. it gathers both upstream and downstream line performance statistics)—therefore the data to perform dynamic line management (DLM) is available at the local node and it should be most efficient if this data can be processed locally at the distribution points, and any subsequent change of DLM profile implemented locally. This approach also allows macro decisions on DLM profile choice to be made by gathering data from neighboring nodes. All of this would be possible with a central data collection system, but this would add to the operations, administration, and maintenance overhead that the network has to carry and requires a data warehouse and large central processing capabilities. 
         [0037]    Each distribution point has to transmit the periodically-gathered statistics back to a remote data collector associated with the central management function  18 . 
         [0038]      FIG. 4  depicts a node  1  (distribution point) having a wired connection  30  to customer premises equipment  2  and an optical connection  32  to a Digital subscriber line access multiplexer (DSLAM)  31 . Each wired customer connection is connected to an xDSL Transmission Unit (Optical) (XTU-O)  16 , and the optical connection  32  is connected through an optical network unit (ONU)  15 . These are interlinked by a interface unit  17  for handling functionality at levels 2 and 3 of the standard OSI seven-level model, under the control of a dynamic line management system  18 . This function includes the multiplexing/demultiplexing of the various customer lines over the optical connection  32 . Having a local Dynamic line management system  18  in each node reduces the requirement for processing power, memory storage requirements, and communications back to a central DLM controller. 
         [0039]    It should be understood that the implementation depicted in  FIG. 4  is an example. The functional elements are shown as co-located for convenience, but some functions may in practice be performed centrally by the DSLAM or in some distributed system. In particular, it should be noted that in a system such as that shown in  FIG. 1 , where there is little or no computational capability in the distribution points  1 , the invention would be implemented in the exchange  39 , with possible local inputs from the customer premises terminals. 
         [0040]    The dynamic line management system may be operated under the control of a multi-layer perceptron (neural net) as described in the applicant&#39;s co-pending International application entitled  Management of Telecommunications Connections , claiming priority from European Patent application 09250095.8, and filed on the same date as the present application.