Patent Publication Number: US-2015086209-A1

Title: Arrangement in a Mobile Network

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to an arrangement in a mobile network for connection of a site node to a central node. 
     BACKGROUND 
     The network solutions of today become more complex due to increase of services and equipment. Mobile site nodes and other types of access sites hold various equipment. The number of access technologies increases, typically today including GSM, GPRS, EDGE, 3G/WCDMA, LTE, WiFi, Wireless PAN (Personal Area Network) and other technologies from IEEE (Institute of Electrical and Electronics Engineers), just to name a few. Furthermore, the telecom operators operating the networks, require that different equipment from different vendors must be able to co-exist and to interoperate. A normal base station of today terminates a variety of networks and services, such as voice and data traffic. The equipment in a single site node may be supplied by different vendors, because an operator may want to enable competition between different vendors, or to equip the site node with the suitable equipment. 
     Furthermore, the increase of usage of mobile services, creates a need for higher capacity in mobile networks. One way to increase the capacity of a mobile network is to increase the capacity of existing site nodes by addition of base stations, antennas and radio unit equipment and corresponding bandwidth to the site nodes. Another way to provide higher capacity in the mobile network is to provide additional site nodes, and thereby create a higher density of the network. 
     The demand for higher bandwidth of mobile data services such as 3G/HSPDA and LTE, increases the need of high bandwidth in the so-called backhaul connection, i.e. the connection from a site node to a core network. The access technologies for connecting site nodes to a core network include wireless connections, various electrical cables and fiber optics. A general tendency is to optical connect site nodes to core networks, it is however today a fragmentation of access solutions. 
     The growth of the number of base stations, as well as access technologies for termination of mobile devices has increased in the past and will continue to increase due to increasing traffic in the networks. This leads to not only an increased number of various kind of base station and radio units in the access network, but also a growth of equipment for operations and maintenance as well as for operation of the backhaul network itself. Normally a site node is connected via a switch or a router to the core network. An example is shown if  FIG. 1 . A typical backhaul connection in practice is redundant, i.e. the communication may go optional ways, if one connection for some reason breaks down. Furthermore, switches and/or routers that connect base stations to the core network also have the task to prioritize and shape the data traffic to and from a single base station. Furthermore, base stations may be cascade connected in rural areas, to minimize the cost of digging. 
     The cost of building and operation of mobile networks increases. The cost for increased bandwidth is justified by increased usage of services, which operators can charge consumers for. However, the cost for increased complexity is undesired by operators. The costs relate to operation and maintenance of the backhaul network, including switches and routers surveillance and repair/replacements, as well as configuration and re-configuration of these switches and routers. 
     SUMMARY 
     It is an object of the invention to address at least some of the problems and issues outlined above. It is possible to achieve these objects and others by using an arrangement and nodes as defined in the attached independent claims. 
     According to one aspect, an arrangement in a network is provided comprising a site node arranged to comprise a base station, with the base station adapted for termination of wireless communication, and a central node arranged to comprise a service unit where the service unit is adapted for communication with the base station. The central node comprises a central switch unit, adapted for switching of data between the base station and the service unit. The base station and the central switch unit are optically connected, thus enabling that communication is carried by light. 
     An advantage with the optical connection, between the base station and the central switch unit is redundancy of active equipment. Costly electric switches may be avoided in a site node, and thereby may the initial cost of acquisition and cost of operation and maintenance be avoided for switch units in site nodes. Another advantage is that configuration, operation and maintenance of an access network may be simpler, because such network related tasks may be concentrated to a central switch unit. 
     According to another aspect is a central switch unit in a central node for switching of data provided. The central switch unit is adapted for switching of data between a base station and a service unit. The central switch unit has an interface for connection of the service unit and an interface for connection of the base station. The interface for connection of the base station is an optical interface for optical communication with the base station. 
     An advantage with a central switch unit, is that a central switch unit may be arranged to handle in principle all switching related to both a central node and a site node. Thus may the central switch unit make any site node located switch unit redundant, and thereby save costs for site node located switches. Another advantage with a central switch unit, may be that concentration of switching to the central switch unit enable better utilization of switching capacity. A site located switch may typically not be well utilized, due to requirements to handle peak traffic. 
     According to another aspect is a central filter unit in a central node provided. The central filter unit comprising an interface for optical connection of a site filter unit, and an interface for optical connection of a central switch unit. The central filter unit is arranged for optical connection of a site filter unit with a central switch unit, such that a base station can optically communicate with the central switch unit. The central filter unit guide light waves between the base station and a corresponding port on the interface of the central switch unit associated with the base station. 
     According to another aspect is a site filter unit in a site node provided. The site filter unit comprising an interface for optical connection of a base station, and an interface for optical connection of a central filter unit. The site filter unit is arranged for optical connection of the central filter unit with the base station, such that the base station can optically communicate with a central switch unit. The site filter unit guide light waves between the base station and a corresponding port on the interface of the central switch unit associated with the base station. 
     An advantage with an arrangement with a central filter unit and/or a site filter unit, is that passive equipment, such as filter units typically may be cheaper in both acquisition as well as operation and maintenance, compared with active equipment such as switching units. Another advantage related to costs, may be that fact that passive equipment, in the absence of active electronics, may have a longer life time, than active electronics. Thus may replacement intervals be longer for filter units compared with switch units. 
     The above arrangement, central switch node, central filter node and site filter node may be configured and implemented according to different optional embodiments. In one possible embodiment, the arrangement is the connection between the base station in the site node and the central switch unit a direct optical connection. In another embodiment is the connection between the radio unit in the site node and the digital unit is a direct optical connection. In another embodiment is the connection between any of the units in the site node and the central switch unit or the digital unit associated with the same light wave length through the entire connection. In another embodiment is the connection between any of the units in the site node and the central switch unit or the digital unit associated with different light wave lengths through the connection, and the wave length is shifted by at least one wave length shifting unit. In another embodiment does the site node comprises a plurality of base stations, radio units, and/or other service termination units, all optically connected to the central switch unit or the digital unit and allocated individual wave lengths. 
     In one possible embodiment the central switch unit may be arranged to connect a plurality of base stations in a site node. In another embodiment is the central switch unit arranged to connect a plurality of site nodes. In another embodiment is the central switch unit arranged to connect a plurality of digital units. In another embodiment is a plurality of base stations and/or radio units associated with the same site unit are connected to a virtual switch unit within the central switch unit. In another embodiment comprises the central switch at least one virtual switch for each type of service. 
     In one possible embodiment is the central filter unit adapted for connection to a plurality of base stations. In another embodiment is the central filter unit adapted for connection to a plurality of base stations from a plurality of site nodes. In another embodiment is the core filter unit adapted for connection to a data packet switching unit. In another embodiment is arrayed waveguide grating used to separate individual light wave lengths. 
     In one possible embodiment can a plurality of site filter units be cascade connected, enabling such that a plurality of site nodes becomes cascade connected. 
     Costs from both acquisition of site node located switches, as well as operation and maintenance of a network for connection of site nodes to a central node, may be advantageously reduced, by optically connecting base stations and other units in a site node to a central node. 
     Further possible features and benefits of this solution will become apparent from the detailed description below. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram, according to the prior art. 
         FIG. 2  is a block diagram illustrating an arrangement in a network. 
         FIG. 3  is a block diagram illustrating a central switch unit and a site switch unit in a network. 
         FIG. 4  is a block diagram illustrating embodiments of an arrangement in a network, and embodiments of a central switch unit, central filter unit, and site filter unit. 
     
    
    
     DETAILED DESCRIPTION 
     Briefly described, a solution is provided to enable an optical connection between a base station and a central switch unit. Today&#39;s solutions of how to build a mobile access network are technically working. However, with the increasing number of base stations and radio units in a network, for handling of the increasing number of subscribers and data traffic, not only the number of units increase, but also the network complexity. In order to minimize technical complexity and costs, it is a desire to limit the amount of equipment in site nodes. The site node describes the facility where base stations and radio units are located, together with supporting and monitoring equipment. 
     A more complex access network increases the complexity of the network architecture in terms of network management and configuration, traffic prioritization, fault handling, etc. An example that searching for a fault becomes more difficult in a network with many individual units. Another example is that a network with virtual network paths becomes within the physical network, becomes more complex than a pure physical network. On the other side, the cost of optical networks is however decreasing. It is therefore an object with the described solution to utilize optical networks to move active network equipment from site nodes in the mobile access network, to more central located nodes in the network. By removing active network equipment like switches and routers, and replacing them with passive optical equipment, it is possible to decrease costs of the equipment itself, as well as costs for operations and maintenance. Obviously switching and routing functionality is needed at some point, but by moving the equipment into more central positions, it is possible to aggregate traffic and better utilize traffic capacity in central located equipment over time. With more simple networks architecture follows limitations on operations and maintenance costs. 
     According to the described solution, various units in a site node are connected to an optical network, where each unit may be associated with an individual wave length. The site node is according to the solution optically connected to a central node in the network, and at the central node switching and routing of data packets, traffic shaping, prioritization, separation, etc, is performed. Thereby it is possible to remove electronic equipment from site nodes and various points in the access network, electronic equipment which is costly itself, costly to configure into the network and has a limited life time. Instead the communication is performed via the passive optical network. 
     An example of an arrangement in a network will now be described in more detail.  FIG. 2  shows a network  10 , with a site node  100  and central node  140 . The site node  100  comprises a base station  120 , and the central node  140  comprises a central switch unit  155  and a service unit  160 . 
       FIG. 2  shows a site node  100 , with a base station  120  and related antenna  130 . A site node  100  may be exemplified by a small facility within a building, suitable for housing of a base station  120 , a facility mounted on a building, e.g. typical on top of the roof of a large building, or a standalone facility, which comprises a base station  120  and an antenna  130 , for termination of wireless communication. The site node  100  may also include additional related equipment.  FIG. 2  further shows the central node  140 . The central node  140  may be located centrally in a network. The central node  140  may also be referred to as central office, main site or core node, to give a few examples. The central switch unit  155  is connected to the base station  120 . The central switch unit  155  may be arranged for switching of data packets. Examples of data packets are Ethernet frames, IP packets (Internet Protocol packets), or similar. The central switch unit  155  is connected to the service unit  160 . The service unit  160  may be arranged for control of a base station  120 , switching of voice traffic, data traffic shaping, or similar core network features. 
     The connection, shown in  FIG. 2 , between the base station  120  and the central switch unit  155  is an optical connection, and thereby enabling that communication is carried by light. 
     As illustrated in  FIG. 2 , the central switch unit  155  has an interface for connection to the service unit  160 , and an interface for connection to the base station  120 . The interface for connection to the base station  120  is an optical interface, such that communication is performed by light between the base station  120  and the central switch unit  155 . 
       FIG. 3  shows a central filter unit  150  in the central node  140 , and a site filter unit  110  in the site node  100 . 
     The site filter unit  110  is arranged to filter the optical communication between the base station  120  and the central filter unit  150 . The site filter unit  110  has an interface for optical connection to the base station  120  and an interface for optical connection to the central filter unit  150 . The site filter unit  110  is arranged to guide light waves, associated with the base station  120 , to a corresponding port on a central switch unit  155 . 
     The central filter unit  150  is arranged to filter optical communication between the site filter unit  110  and the central switch unit  155 . The central filter unit  150  has an interface for optical connection to the site filter unit  110  and an interface for optical connection to the central switch unit  155 . The central filter unit  150  is arranged to guide light waves, associated with the base station  120 , to a corresponding port on a central switch unit  155 . 
       FIG. 4  shows embodiments of an arrangement in a network, embodiments of the site filter unit  110 , central filter unit  150  and the central switch unit  155 . 
     According to an exemplifying embodiment, a site node  100  comprises a plurality of base stations  120 . A plurality of base stations  120  may serve a larger number of subscribers than a single base station  120 , or higher voice and/or data traffic capacity than a single base station  120 . A base station  120  has one or more ports for network connection, for provision of redundancy, robustness, etc. Such ports may, as a non-limiting example, be supporting e.g. Ethernet or IP. Each port may be associated with an individual light wave length. 
     A site node  100  may alternatively or in addition comprise one or a plurality of radio units  220 , for termination of wireless communication. A radio unit  220  may also be described with the term remote radio unit, or base band unit, not limiting this description to use of other terms. Such a radio unit  220  is optically connected to the site filter unit  110 , via one or a plurality of ports. The plurality of ports for provision of redundancy, robustness, etc. Such connection may be carried by the CPRI-protocol (Common Public Radio Interface). Each port may be associated with an individual light wave length. The other end of the optical communication may be a digitalization unit  240 . The digitalization unit  240  may for example convert the digitalized analogue signal to GSM/3G or VoIP. 
     According to an exemplifying embodiment the site node  100  may comprise a support unit  230 , or a plurality of support units  230 . Examples of support units  230  are climate control unit in the site node  100 , intrusion control unit in the site node  100 , alarm monitor unit for monitoring of alarms from other units in the site node  100 , power supply unit for power supply to other units in the site node  100 , etc, not limiting other functions of a support unit  230 . The support unit  230  may be connected to the site filter unit  110  via an optical connection. 
     The central node  140  may comprise an operation and maintenance unit (O&amp;M)  235 . Supporting units  230  may be optically connected to an operation and maintenance unit  235 . Supporting units  230  may also be communicating with the operation and maintenance unit  235 , connected via the central switch unit  155 . For example, different kind of supporting units  230  may be optically connected to different kind of operation and maintenance units  235 , possibly via the central switch unit  155 . The different kinds of operation and maintenance units  235  may be associated with specific tasks performed by the different kind of supporting units  230 . 
     Different types of units may be associated with different groups of light wave lengths. An example: base stations  120  may be associated with the red spectrum of light waves, radio units  220  may be associated with the green spectrum of light waves, support units  230  may be associated with the blue spectrum of light waves. Alternatively or in addition, units belonging e.g. to different network operators may be associated with different groups of light wave lengths. It is today rather common for competing operators to share site nodes and/or antenna masts, to save costs or by authority requirements. Thereby, different units belonging to a specific operator could be associated with a group of light wave lengths or by other means. An example; all base stations  120 , all radio units  220 , and all support units  230  owned by the same operator, may be associated to a common light wave group or a spectrum. A plurality of site filter units  110  may be cascade connected. A port on the site filter unit  110  may be allocated for another site filter unit  110 . An example is a rural area where one or a plurality of site nodes  100 , which are remotely located, are connected to a site node  100 , which is located at the access network. The option is to extend the access network with individual connections to the more remotely located site nodes  100 , but to the expense of more digging or air lines. 
     One or more measurement units  295  may be arranged in the optical connection, between the site filter unit  110  and the central filter unit  150 . The measurement unit  295  may measure quality of optical signals. The measurement unit  295  may also measure the quality of a part of the communication. The measurement unit  295  may also measure the quality of all signaling on a single fiber, or, the quality of the signals in a plurality of fibers. There are a number of quality parameters which may be measured. It is however known by the person skilled in the art, which parameters that may be measured and therefore not further described in this description. 
     A shifting unit  290  may be arranged in the optical connection. The shifting unit may be shifting one light wave length to another light wave length. In an embodiment a plurality of shifting units  290  are arranged in the optical network. Such shifting is, however, known to the person skilled in the art, and will therefore not be further described herein. 
     According to an embodiment, as shown in  FIG. 4 , is the central filter unit  150  located in the central node  140 . The central filter unit  150  may be connected to the site filter unit  110 . An example of such connection is a single fiber, carrying a plurality of light wave lengths. Typically, a single fiber may carry up to approximately 80 wave lengths, or up to approximately 480 wave lengths, or a range between 2 and approximately 2 000 wave lengths. The single fiber may as well carry only one wave length. In another embodiment a plurality of fibers are connected to the central filter unit  150 , from the site filter unit  110 . An advantage with at least two fibers connected to the central filter unit  150 , from the site filter unit  110 , is that if one fiber is cut off for any reason, the other one may carry the communication. 
     According to an exemplifying embodiment, a plurality of site filter units  110  are connected to a single central filter unit  150 . An example is where a site node  100  comprises a plurality of site filter units  110 . Another example is where a plurality of site nodes  100 , with a plurality of site filter units  110 , are connected to a single central filter unit  150 . 
     The central filter unit  150  may be connected to a central switch unit  155 . The central filter unit  150  may also be connected to a digital unit  240 . In an embodiment there may be a plurality of central filter units  150  connected to a plurality of central switch units  155 . In another embodiment a plurality of central filter units  150  also are connected to a plurality of digital units  240 . These should only be seen as examples of various combinations, where the demand for redundancy or capacity will determine the number of units in a solution. 
     According to an exemplifying embodiment, a plurality of base stations  120  are connected to the central switch unit  155 . The communication between the base stations  120  and the central switch unit  155  is optical. The central switch unit  155  may comprise at least one virtual switch unit. A virtual switch unit may replace a switch that traditionally is located in the site node  100 . I.e. a virtual switch unit may be switching traffic between different units within a site node  100 . An example is switching of data packets between a base station  120  and a support unit  230 . Another example is switching of data between two different base stations  120  within the same site node  100 . In another embodiment are similar services operated in different site nodes  100  associated to the same virtual switch. An example is VoIP-traffic (Voice-over-Internet Protocol) from base stations  120  in different site nodes  100 , directed to and switched in the same virtual switch. Another example is where GPRS (General Packet Radio Service) or HSDPA (High-Speed Downlink Packet Access) traffic from base stations  120  from a plurality of site nodes  100 , is switched in the same virtual switch. 
     According to an exemplifying embodiment, the central switch unit  155  is arranged to switch native Ethernet. The central switch unit  155  may also be arranged to switch Ethernet over VLAN (Virtual Local Area Networks). The central switch unit may also be arranged to switch in accordance with MPLS-switching (Multi Protocol Layer Switching). The central switch unit  155  may also be arranged to act as a router, and route IP (Internet Protocol) packets, according to various static or dynamic routing methods. 
     According to an exemplifying embodiment, the central switch unit  155  may have sensing capabilities. Such sensing capabilities may be able to detect what kind of protocol that is used by equipment connected to the switch, protocols such as Ethernet, CPRI, or other protocols. The sensing capabilities may also be able to detect equipment of a certain kind or from a certain vendor. The central switch unit  155  may have similar sensing capabilities. The sensing capabilities may, for example, be used to determine if a connection is provided to a desired port or not, to the central switch unit  155 . The sensing capabilities may, for example, be used to determine how to automatically switch traffic connected to a port on the central switch unit  155 . 
       FIG. 4  shows the service unit  160 . The service unit  160  operates services which are terminated by a base station  120  or a radio unit  220 . The service unit  160  is connected to the central switch unit  155 . Other units that may be connected to the central switch unit  155 . Examples of such units are Mobile Gateway (MGW)  270 , and/or Mobile Soft Switch (MSS)  272 , and/or Serving GPRS Node (SGSN)  274 , not limiting other units or nodes to be connected to the central switch unit  155 . 
     While the solution has been described with reference to specific exemplary embodiments, the description is generally only intended to illustrate the inventive concept and should not be taken as limiting the scope of the solution. For example, the terms “central switch unit”, “central filter unit” and “service unit” have been used throughout this description, although any other corresponding nodes, functions, and/or parameters could also be used having the features and characteristics described here. The solution is defined by the appended claims.