Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/02—Power saving arrangements
  • H04W52/0203—Power saving arrangements in the radio access network or backbone network of wireless communication networks
  • H04W52/0206—Power saving arrangements in the radio access network or backbone network of wireless communication networks in access points, e.g. base stations
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
  • H04W52/04—TPC
  • H04W52/38—TPC being performed in particular situations
  • H04W52/46—TPC being performed in particular situations in multi hop networks, e.g. wireless relay networks
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
  • H04W88/08—Access point devices
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
  • Y02D30/00—Reducing energy consumption in communication networks
  • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

• the present invention relates to a method for energy saving in a communication system. Furthermore, the invention also relates to a computer program, and a computer program product, and a control device.
• Cellular communication systems are designed for peak hour traffic despite the fact that the traffic activity in a certain area normally is high only during short periods of the day. Considering the traffic activity in a residential area, it is usually low during daytime when people have left homes for work while it increases in the evenings when people are at home. The opposite pattern prevails for an office area. In a heterogeneous network environment different infrastructures are differently utilised throughout the duration of a day, e.g. macro cells are serving traffic in a residential area during working hours while a vast amount of the traffic is carried by pico or femto cells during evenings and late hours.
• the radio network could be a heterogeneous network (HetNet) consisting of sites with different power transmission, coverage and capacity profiles.
• HetNet heterogeneous network
• One of the key optimisation problems in such HetNet scenario is to maximize or maintain user throughput and coverage at a minimum of energy consumption cost.
• the density of cell sites must increase to meet growing traffic demands.
• Many of the nodes will be low power nodes with limited coverage but high capacity.
• a major deployment and operating expense for such low-cost nodes is the backhaul provision. In many cases wired backhaul using fibre or coaxial cable is not an economically viable option. Instead wireless backhaul is gaining attention as a lower cost alternative.
• FIG. 1 shows a typical wireless access network with meshed wireless backhaul.
• the access nodes communicate directly with mobile stations and the traffic is backhauled to a neighbouring mesh node.
• the meshed nodes are wirelessly linked together to reach a single gateway node in this example.
• Access nodes with low power are typically attached to the side of buildings whilst the mesh nodes often are raised higher and placed on roof-tops. More elaborate networks could include: backhaul via a neighbouring access node and integration of access node and mesh node, which is illustrated in figure 2.
• An object of the present invention is to provide a solution which mitigates or solves the drawbacks and problems of prior art solutions relating to energy saving.
• an object of the invention is to provide a solution which minimizes the total power consumption of access nodes and backhaul nodes.
• the above mentioned objects are achieved by a method for energy saving in a communication system, said communication system including: at least one wireless access network comprising one or more wireless access nodes and one or more mobile stations, and
• At least one associated wireless backhaul network comprising one or more wireless backhaul nodes; said method comprising the steps of:
• control device for a communication system said communication system including:
• At least one wireless access network comprising one or more wireless access nodes and one or more mobile stations, and
• At least one associated wireless backhaul network comprising one or more wireless backhaul nodes
• control device is arranged to control said one or more wireless access nodes and said one or more wireless backhaul nodes; and said control device further being arranged to:
• Fig. 1 shows an example of a wireless meshed backhaul
• Fig. 2 shows an example of a more sophisticated wireless meshed backhaul architecture
• FIG. 3 shows an exemplary scenario in a communication network
• Fig. 4 shows a communication network before energy saving
• Fig. 5 shows a communication network after energy saving
• Fig. 6 illustrates some different connectivity options. Detailed Description of the Invention
• the present invention relates to a method for energy saving in a communication system of the type including at least one wireless access network comprising one or more wireless access nodes (ANs) and one or more mobile stations; and further at least one associated wireless backhaul network comprising one or more wireless backhaul nodes (e.g. meshed backhaul nodes, MNs).
• the present communication system can e.g. be a communication system according a 3GPP standard or any other suitable system, and the wireless access nodes may e.g. be base stations, remote radio heads, relay stations, or any other suitable communication devices with corresponding function(s).
• the wireless backhaul network is a mesh network according to preferred embodiment of the present invention, which is illustrated in the appended figures.
• the present method comprises the steps of: controlling a first power consumption P of the one or more wireless access nodes, and jointly controlling a second power consumption P 2 of the one or more wireless backhaul nodes such that a sum P Sum . of the first power consumption P and the second power consumption P 2 is minimised.
• the first power consumption P is preferably the total power consumption of the one or more wireless access nodes
• the second power consumption P 2 is preferably the total power consumption of the one or more wireless backhaul nodes.
• an access network configuration is e.g. the on/off settings of the nodes (or cells) of the network.
• the backhaul configuration considers e.g. the on/off settings and also the network topology, e.g. which node connects to which other node(s).
• the steps of controlling of the present method involves switching the one or more wireless access nodes and the one or more wireless backhaul nodes between energy saving mode and non-energy saving mode.
• the energy saving mode and the non-energy saving mode may be ON-mode and OFF-mode, respectively, which means that the nodes are either in on or off state.
• the energy saving mode could also relate to different energy consumption levels. For example, when the full capacity of a node is not needed, the node may be configured with sleep periods and active periods. During the sleep periods parts of the node are switched to a low energy state, and no data can be sent or received. All data reception and transmission is performed during the active periods of the node. In another example of a node in energy saving mode, the capacity may be reduced by switching off some antennas while maintaining continuous service.
• access network configuration A meshed network configuration D is the best (lowest) for total power consumption with the present joint optimisation method.
• the access network with the highest power consumption gives the lowest total power consumption in this particular example.
• Access Network Power Meshed network Power Total power Configuration consumption configuration (best consumption consumption for access network
• the access node power consumption includes a component for its backhaul link(s) have been ignored and this may vary according to which mesh node(s) it connects to.
• the sum power consumption (P + P 2 ) may further depend on:
• Access network configuration which access nodes are in energy saving mode, type of energy saving mode, which mobile connects to which cell, etc.
• Association of access nodes to backhaul nodes i.e. for each active access node which backhaul node(s) does it connect to.
• Figure 3 a new mobile station wants to connect to the internet. Its closest AN is AN3 but this is currently switched off (sleeping). Also, if AN3 is enabled then meshed node MN3 must be switched on to allow backhaul. The alternative is to force the mobile to connect to AN2. This choice probably has lower total power consumption although consumption for that specific mobile station will be larger.
• FIGs 4 and 5 in the example in figure 4 ANl and AN2 are lightly loaded while AN3 is heavily loaded. It makes sense to switch off ANl or AN2. If ANl is switched off then MN1 can also be switched off so this will save the most total energy. This energy saving state is illustrated in figure 5.
• a central entity e.g. an optimization server in network management system
• a central entity could determine the optimum state of the complete network using standard optimization techniques such as simulated annealing. For example, if a mobile station is assumed to connect to its nearest AN, and each AN connects to its nearest MN (only), and the mesh nodes are fully meshed, then the state of the system can be described as an on/off vector of length equal to the sum of the number of ANs and the number of MNs. The power consumption of each possible vector value would be estimated and the search would look for a global minimum in this space.
• a constraint that certain minimum Quality of Service (QoS) should be met may be added, hence the sum P Su m is minimised subject to at least one QoS requirement for mobile stations in the access network.
• the QoS requirement may relate to any of: latency, cell downlink throughput, cell uplink throughput, cell edge downlink throughput, cell edge uplink throughput, or traffic QoS. Since the QoS requirement of the mobile stations may vary, only taking into account the presence of mobile stations at certain locations does not give a very accurate view of the required capacity. Therefore, adding constraints for the specific services of each mobile station at a given time will allow a more accurate optimization of the energy consumption for a required service level.
• the AN can connect to one of several MNs,
• the AN can connect to multiple MNs simultaneously,
• the backhaul network is a mesh network
• the mesh is not fully-meshed but the enabled links and nodes should be chosen considering the optimisation.
• the optimization should be performed regularly as mobile stations move or new mobiles transition to/from active state. Even changes in a traffic bearer to one mobile user, e.g. from ftp download to video streaming could induce a re-optimization.
• the rate at which the energy optimization can be performed depends on the speed of the optimization and the speed at which nodes can be reconfigured, e.g. switched on or off. Impacts on mobile stations are also a consideration, handovers that are forced by switching an AN off may impact the perceived Quality of Experience (QoE) of the mobile users.
• QoE Quality of Experience
• a distributed implementation of the optimization would in principle also be possible. This scales better with network size but is likely to give poorer performance compared to a centralised solution.
• the access node may support a steerable antenna for connecting to the backhaul (mesh) nodes in its neighbourhood, either by mechanical or electrical adjustment (such as beam switching) or multiple beams.
• the management of the nodes may be executed using the backhaul link itself.
• the alternative could be to employ a permanent wired communications link to the node such that OAM management or management from a central control entity could take place.
• This link could be of low bandwidth since management traffic is generally light, so fibre would not be necessary.
• the link could possibly be implemented together with the power provision to the node, e.g. using IEEE 1901.
• the management signal could be to switch the access node on.
• the paging could work as follows:
• a backhaul node sends wireless page message to an access node at predetermined time - this could be at one of a periodic set of paging occasions,
• the access node wakes up on every paging occasion and on this occasion it reads the page message
• the access node sends a response to the backhaul node and fully wakes up, and
• the backhaul node sends management signalling to the access node.
• the frequency of paging occasions is a trade off between the time that the nodes need to be in wake up mode and the delay that will be incurred before a node can be paged.
• the backhaul node nearest to the access node may itself be asleep.
• the wake up delay can be reduced by synchronizing the paging occasions of the backhaul nodes and access nodes.
• the access node paging occasions should slightly lag those of the backhaul node to allow the backhaul node to wake-up and then itself to page the access node according to an embodiment.
• the wake up periods for the backhaul nodes lag the wake up periods for the access nodes depending on the scenario.
• the different wake up periods may be synchronised with some time shifts between them.
• the wake up periods of the interfaces of two different nodes that they use to communicate with each other shall wake up at the same time, but when a node has two interfaces in different directions there may be a time lag between the two interfaces. So a mobile station wakes up at the same time as the radio interface of the access node, and one interface of a backhaul node wakes up at the same time as the access node backhaul interface.
• the lag in the wake up periods between different interfaces of a node may be configurable in a way which corresponds to the requirements of control signalling.
• the access node may wake up first and broadcast a reference signal that the mobile stations within its coverage area can detect.
• This access node may be called a probing access node.
• the mobile stations may report the presence of the probing access node to the access node they are currently connected to. Mentioned access node can then decide to trigger the probing access node to wake up and start serving the mobile stations.
• the control signalling will be sent after the wake up of the access node, hence the wake up time of the backhaul nodes would lag that of the access nodes.
• the wake up times can also be used for broadcasting probing signals to detect if there are any mobile stations that may connect to an access node that is in sleep mode.
• the access node wake up times would then be synchronized with the mobile network signalling, and also mobile stations with discontinuous reception (DRX) configuration could have their active periods synchronized with the same wake up times.
• DRX discontinuous reception
• ⁇ For access nodes and mobile stations, e.g. paging occasions, ES probing, etc.
• One advantage of such synchronization is that the on time for all nodes is minimized without reducing the connectivity or causing additional delay. If the wake up periods would not be synchronized the control signalling would either have to be delayed in the access nodes or backhaul nodes or the connectivity opportunity would be lost. Alternatively, longer wake up periods would be needed for non-synchronized nodes to guarantee that the nodes would have overlapping wake up times and thereby allow the nodes to connect.
• any method according to the present invention may also be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method.
• the computer program is included in a computer readable medium of a computer program product.
• the computer readable medium may comprises of essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.
• the present invention also relates to a control device arranged to control one or more wireless access nodes of at least one wireless access network and one or more wireless backhaul nodes of at least one associated wireless backhaul network.
• the control node is further arranged to control a first power consumption P of the one or more wireless access nodes, and jointly control a second power consumption P 2 of the one or more wireless backhaul nodes such that a sum P Su m of the first power consumption and the second power consumption is minimised.
• the control device above may be modified, mutatis mutandis, according to different embodiments of the present method.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

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• 2012
  • 2012-08-31 CN CN201280075270.8A patent/CN104604302A/zh not_active Withdrawn
  • 2012-08-31 WO PCT/EP2012/067021 patent/WO2014032733A1/en active Application Filing

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