ONU with wireless connectivity capability

The embodiments herein relate to a method in an optical network unit (103), referred to as an ONU, for providing wireless connectivity capability to the ONU (103). The ONU (103) is comprised in a communications network (100). The ONU (103) is interconnected to an optical line terminal (101), referred to as an OLT, via a wireline communications link (104) and a wireless communications link (113). The ONU (103) is configured to support a sleep mode. The ONU (103) obtains information about entry into the sleep mode. The ONU (103) identifies whether the wireless communications link (113) is activated or deactivated, and activates the wireless communications link (113) if the wireless communications link (113) is identified as deactivated. The ONU (103) enters sleep mode, and provides wireless connectivity capability to the ONU (103) by means of the wireless communications link during the sleep mode.

TECHNICAL FIELD

Embodiments herein relate generally to an Optical Network Unit (ONU) and a method in the ONU, an Optical Line Terminal (OLT) and a method in the OLT and a method in a communications network.

More particularly the embodiments herein relate to providing wireless connectivity capability to the ONU.

BACKGROUND

A Passive Optical Network (PON) is a point-to-multipoint network architecture that brings optical fiber cabling and signals all or most of the way to the end user. A PON comprises an OLT at a service providers Central Office (CO) and a number of ONUs near end users. More than one ONU may be connected to the same OLT by means of passive or in some cases, active, intermediate elements. For example, up to 32 ONUs may be connected to an OLT. PONs are called passive because optical transmission requires no power or active electronic components. In other words, other than at the central office and subscriber/user endpoints, there are typically no active electronics within an access network. An access network is that part of a communications network which connects subscribers to their immediate service provider. It is contrasted with the core network. The core network is the central part of the communications network that provides various services to subscribers who are connected by the access network. Downstream signals, i.e. from the OLT to the ONU, are broadcasted to all users sharing a single fiber. Upstream signals are signals transmitted from the ONU to the OLT.

An ONU is a device that converts incoming downstream optical signals transmitted from the OLT via a wireline fiber optical communications channel, referred to as an optical link, into electrical signals. These electrical signals are then sent to individual subscribers over an optical fiber network, in order to provide telecommunications services. An ONU comprises an optical transceiver. The ONU may also be called an Optical Network Terminal (ONT), which is a special case of an ONU that serves a single subscriber.

As mentioned above, the ONU is used in combination with the OLT. The OLT performs conversion between the electrical signals used by the service provider's equipment and the fiber optic signals used by the PON. The OLT coordinates the multiplexing between the ONUs at or near the various subscriber locations.

PON system energy conservation has been embraced by the International Telecommunication Union (ITU) as a necessary goal. One target of the ITU is to explore potential solutions to improve energy conservation through reduced power consumption within optical access networks. These solutions may have impact on improving the equipment performance and service longevity in battery-powered operation, as well as on energy conservation and CO2emission in general.

The term power refers to the ability to do work, while the term energy is a measure of the amount of work done, that is, power time. Therefore, energy may be saved or conserved, while power may be reduced. Throughout the industry, the term power is commonly used to refer to both. It is to be understood in the following description that terms such as power saving imply power reduction for a period of time, with the purpose of energy saving.

Wireless communication is a fast growing segment of the communications industry. Wireless cellular systems have experienced exponential growth over the last decade. Many new applications are emerging from research ideas to concrete systems. This explosive growth of wireless systems coupled with the proliferation of devices such as smart phones indicate a bright future for wireless networks.

A current power saving mode conserves energy by implementing sleep cycles to completely power off the ONU optical transceiver at certain times. Thus, at any given time, the ONU may be in so-called sleep mode or so-called awake mode, and it may use a wake-up timer to change between the modes. In order to support ONU wake-up, sleep cycles are provisioned by the OLT, typically in the order of 10-100 milliseconds. Only when the sleep cycle expires, does a sleeping ONU have the chance to wake up to receive downstream traffic. During a sleep period, the OLT may buffer downstream traffic destined to the ONU. When there is no downstream traffic to a sleeping ONU, the ONU still has to be awakened when the wake-up timer expires, i.e. when the sleep interval expires. Frequently turning the optical transceiver on and off contributes to extra power consumption. When there is downstream traffic destined to an ONU, and the ONU is still in sleep mode, the OLT has to buffer the traffic until the wake-up timer expires. The necessary buffer memory adds cost and power consumption to the OLT.

Another power saving mode is power shedding, in which non-essential services are switched off when the ONU goes into battery operation mode after e.g. an alternating current (AC) power failure. Power shedding has the target to reduce the demand for battery power and prolong the survival time of the ONU, while still maintaining lifeline Plain Old Telephone Service (POTS). The current definition of power shedding mode still maintains the optical transceiver on, while just powering down other selected elements in the ONU. However, one of the main power consumption contributors in the ONU is the optical transceiver module. Additional energy may be saved by combining power shedding with sleep mode.

SUMMARY

The objective of embodiments herein is therefore to obviate at least one of the above disadvantages and to reduce power consumption in the communications network.

According to a first aspect, the objective is achieved by a method in an optical network unit, referred to as an ONU, for providing wireless connectivity capability to the ONU, which ONU is comprised in a communications network. The ONU is interconnected to an optical line terminal, referred to as an OLT, via a wireline communications link and via a wireless communications link. The ONU is configured to support a sleep mode. The ONU obtains information about entry into the sleep mode. The ONU identifies whether the wireless communications link is activated or deactivated, and activates the wireless communications link when the wireless communications link is identified as deactivated. The ONU enters sleep mode, and provides wireless connectivity capability to the ONU by means of the wireless communications link during the sleep mode.

According to a second aspect, the objective is achieved by a method in an optical line terminal, referred to as an OLT, for providing wireless connectivity capability to an optical network unit, referred to as an ONU, which OLT is comprised in a communications network. The OLT is interconnected to the ONU via a wireline communications link and via a wireless communications link. The OLT identifies bearer traffic to the ONU when ONU is in a sleep mode. The OLT buffers the identified bearer traffic. The OLT transmits information about exit out of sleep mode to the ONU via the wireless communications link. The OLT transmits, after the ONU has exited sleep mode, the buffered bearer traffic to the ONU using the wireline communications link, and provides wireless connectivity capability to the ONU by means of the wireless communications link during the sleep mode.

According to a third aspect, the objective is achieved by a method in a communications network for providing wireless connectivity capability to an optical network unit, referred to as an ONU. The communications network comprises an optical line terminal, referred to as an OLT. The OLT and the ONU are interconnected via a wireline communications link and via a wireless communications link. The OLT and the ONU is configured to support a sleep mode. The communications network exchanges control or management data or bearer traffic between the OLT and the ONU over the wireline communications link when the ONU is out of sleep mode, i.e. it is in awake mode. The communications network exchanges control or management data and bearer traffic between the OLT and the ONU over the wireless communications link when the ONU is in the sleep mode. The communications network provides wireless connectivity capability to the ONU by means of the wireless communications link when the ONU is in the sleep mode.

According to a forth aspect, the objective is achieved by an optical network unit, referred to as an ONU, for providing wireless connectivity capability to the ONU. Which ONU is comprised in a communications network. As mentioned above, the ONU is interconnected to an optical line terminal, referred to as an OLT, via a wireline communications link and via a wireless communications link. The ONU is configured to support a sleep mode. The ONU comprises an obtaining unit configured to obtain information about entry into the sleep mode and an identifying unit which is configured to identify whether the wireless communications link is activated or deactivated. Further, the ONU comprises an activating unit which is configured to activate the wireless communications link if the wireless communications link is identified as deactivated. The ONU comprises an entering unit configured to enter sleep mode, and a providing unit which is configured to provide wireless connectivity capability to the ONU by means of the wireless communications link during the sleep mode.

According to a fifth aspect, the objective is achieved by an optical line terminal, referred to as an OLT, for providing wireless connectivity capability to an optical network unit, referred to as an ONU, Which OLT is comprised in a communications network. The OLT is interconnected to the ONU via a wireline communications link and via a wireless communications link. The OLT comprises an identifying unit configured to identify bearer traffic to the ONU when the ONU is in a sleep mode. The OLT comprises a buffering unit which is configured to buffer the identified bearer traffic. Further, the OLT comprises a transmitting unit configured to transmit information about exit out of sleep mode to the ONU via a wireless communications link, and configured to transmit, after the ONU has exited sleep mode, the buffered bearer traffic to the ONU using the wireline communications link.

By integrating a wireless transceiver module into the ONU, it is provided with wireless connectivity capability, which enables improved power consumption in the communications network. The wireless connectivity capability may be utilized in cases such as for example PON signaling, applications handshakes and POTS calls in sleep mode, periodic maintenance, etc.

Embodiments herein afford many advantages, of which a non-exhaustive list of examples follows:

Embodiments herein enable wake up of the ONU in power saving or sleep mode via (wireless connectivity. This provides an adaptive wake-up management by monitoring traffic in the communications network.

When there is no downstream traffic to a sleeping ONU, the ONU may keep sleeping until it receives a wireless wake-up message from the OLT. During an ONU sleep period, no power is consumed by the optical transceiver.

When there is downstream traffic addressed to the ONU, the OLT wakes up the ONU via a wireless notification instead of waiting for a wake-up timer to expire. This improves the quality of service seen by the end user and reduces the amount of buffering needed at the OLT.

Embodiments herein provide the advantage of enabling POTS calls even when the optical transceiver is powered off, and without waking up the ONU. In power saving mode, which comprises e.g. power shedding and power sleeping, shutting down the optical transceiver saves power and prolongs battery availability. During sleep periods, OLT maintenance windows or fiber cut accidents, POTS calls thus remain available for customers, thereby additionally improving the reliability of the service.

Another advantage of embodiment herein is that periodic maintenance messages, such as Session Initiation Protocol (SIP) heartbeat and Internet Group Management Protocol (IGMP) query messages are carried over the wireless link between ONU and application servers without the need to awaken a sleeping ONU.

A further advantage of embodiments herein is that the ONU's wireless module remains in idle mode when there are no wireless messages between the ONU and the OLT, and thus saves additional power. Wireless connectivity consumes less energy than the optical transceiver.

Embodiments herein are not limited to the features and advantages mentioned above. A person skilled in the art will recognize additional features and advantages upon reading the following detailed description.

The drawings are not necessarily to scale and the dimensions of certain features may have been exaggerated for the sake of clarity. Emphasis is instead placed upon illustrating the principle of the embodiments herein.

DETAILED DESCRIPTION

FIG. 1depicts a communications network100. The communications network100comprises a PON and a cellular network. Transmissions within the PON are typically performed between the OLT101and at least one ONU103via a PON wired fiber optical communications link. The PON wired fiber optical communications link will from now on be referred to as the optical link104. The communications network100comprises i number of ONUs103, where i is an integer from 1 upward. Between the OLT101and ONU103there is an Optical Distribution Network (ODN)105which comprises fibers and splitters. The OLT101generally resides in the central office of the operator of the network100, and couples the optical access network to an aggregation network106, through which the OLT101may additionally communicate with a Base Station (BS)108in the cellular network via a wireline communication link109. The wireline communication link109is different from the optical link104. The base station108serves a cell110. The base station108may be a base station such as a NodeB, an evolved NodeB (eNB), or any other radio network unit. The cell110is a geographical area where radio coverage is provided by the base station108at a base station site. Each cell110is identified by an identity within the local radio area, which is broadcast in the cell110.

The ONU103may be located in the residence of a customer. The ONU103may also be of different types having different purposes, such as a Multi-Dwelling Unit (MDU) which is usually used for Fast Fourier Transform (FTT) Building, FTTBusiness and FTTFloor deployment, whereas a Single Family Unit (SFU) ONU is adapted for residential use etc. All of these ONU types may be under the coverage of the cellular network. The ONU103may have a wireless connectivity capability with the Base Station108in the cellular network by integrating a wireless transceiver module with the ONU103. Thus, the base station108has a wireless communication link113to the ONU103.

The cellular network may use technologies such as Long Term Evolution (LTE), Global System for Mobile Communications (GSM), Worldwide Interoperability for Microwave Access (WiMAX), Universal Terrestrial Radio Access Network (UTRAN) etc. It should be noted that the wireless link113between the base station108and the ONU103may use any suitable protocol depending on type and level of layer, e.g. as indicated by the Open Systems Interconnection (OSI) model, as understood by the person skilled in the art.

The user equipment (not shown) may be any suitable communication device or computational device with communication capabilities connected to a wired port of the ONU103. The user equipment may comprise for example a telephone, a Personal Computer (PC), a television etc.

As mentioned above and as illustrated inFIG. 2, the ONU103comprises a wireless transceiver201configured to transmit and receive wireless signaling, system control or management data and bearer traffic to and from the OLT101via the base station108over the wireless link113. By accessing the cellular network using the wireless link113, an alternative communication link between ONU103and OLT101is provided in addition to the optical link104. The ONU103further comprises an optical transceiver203configured to transmit and receive wired optical signals, traffic and data to and from the OLT101over the optical link104. The wavelength of the transmitted optical signals may for example be 1310 nm, and the wavelength of the received optical signals may be for example 1490 nm. As seen inFIG. 2, the ONU103further comprises a processing unit, such as e.g. the Central Processing Unit (CPU)205. The CPU205carries out the functions of the ONU103according to sequential instructions in a program stored in the ONU103. The ONU103comprises a PON Media Access Controller (PON/MAC)207providing addressing and channel access control mechanisms that make it possible for several ONUs103to communicate within the multi-point network that is a PON.

In addition to the wake-up mechanisms defined by for example the ITU, which may be based on timers or local traffic at the ONU103, the ONU103has an adaptive wake-up mechanism using wireless based wake-up signaling. The ONU103may be in different modes, e.g. a sleep mode or an awake mode. The sleep mode may also be referred to as sleep state and the awake mode may also be referred to as awake state. The awake mode may also be referred to as out of sleep mode. These modes may provide e.g. reduced energy consumption. A sleep mode refers to a low power mode, which saves significant electrical energy consumption compared to leaving the optical transceiver device203fully on. The awake mode refers to a state when the optical transceiver device203is on, i.e. the opposite of sleep mode, and in which the ONU103is fully capable of providing all telecommunications services via the optical link104, but with increased energy consumption. In the ONU sleep mode, both the ONU optical transmitter and ONU optical receiver, i.e. the ONU optical transceiver203, are turned off. The wireless transceiver201consumes less energy than the optical transceiver203, and remains active during ONU sleep mode.

The method for providing wireless connectivity capability to the optical network unit103, according to some embodiments will now be described with reference to the combined signaling diagram and flowchart depicted inFIG. 3. The method comprises the following steps, which steps may as well be carried out in another suitable order than described below.

The ONU103is awake, i.e. it is not in any power saving mode, and the wireless transceiver201of the ONU103is deactivated by default.

The wireless transceiver201of the ONU103is activated when the ONU103is ready to enter power saving mode.

During the sleep mode, the ONU103transmits and receives communication to and from the OLT101, using the activated wireless transceiver201, the wireless communication link113and the base station108.

The ONU103may use the wireless transceiver201for different reasons. Some of the reasons may be energy saving requirements from the operator, AC power failure, maintenance of the OLT101, fiber cut of the PON link104etc. Some of these examples are described in more detail below.

The communication may be data traffic, messages, signaling or any other type of communication between the ONU103and the OLT101.

The wireless communication link113may be used for control or management data and high-priority bearer traffic, such as Voice over Internet Protocol (VoIP) traffic.

The ONU103leaves the energy saving mode and enters the awake mode. The reason for the ONU103to leave the energy saving mode may be e.g. restored AC power, timer expiration, etc. In the embodiments herein, an additional reason to awaken is that the ONU receives a wake-up message from the OLT via the wireless link113. This is not possible in a traditional ONU configuration that contains only an optical link104.

During the awake mode, the ONU103communicates with the OLT101via the optical link104, using the optical transceiver203.

Bearer traffic is an example of a type of communication that is communicated via the optical link104. When the ONU103is in awake state, it may use the optical link104for all communications with the OLT101.

The wireless transceiver201may be deactivated when the ONU103leaves the power saving mode. In some embodiments, the ONU may go in and out of sleep mode fairly frequently, and therefore the wireless transceiver201may remain enabled. In other embodiments, where the ONU103is intended to remain awake for an extended period, the wireless transceiver201may be disabled.

The following description provides example embodiments and details of the method described inFIG. 3applied to different types of traffic, i.e. system control traffic, high-priority voice bearer traffic and control or management data. The example embodiments described below areSystem control, e.g. adaptive wake-up mechanism by wireless-based wake-up signaling.High-priority voice bearer traffic, e.g. POTS calls in power shedding and power sleep mode without awakening the optical transceiver.Control or management data, e.g. periodic maintenance messages.
System Control Traffic—Adaptive Wake-Up Mechanism by Wireless-Based Wake-Up Signaling

When the ONU103is in power saving mode, the OLT101may monitor traffic status of all ONUs103in the communication network100that are in sleep mode. When there is enough downstream bearer traffic, e.g. Ethernet traffic, directed to the sleeping ONU103, the OLT101will send a wireless wake-up message via the base station108to the ONU103to turn on the optical transceiver203to receive the buffered downstream bearer traffic. When there is not enough downstream bearer traffic to warrant awakening the ONU103, the OLT101may leave the ONU103in sleep mode. In this way, an ONU103with wireless connectivity113provides an adaptive wake-up mechanism, and thus enables increased power saving.

Traffic that may be transferred via the wireless link113without awakening the ONU103comprises for example, single message exchanges such as keep-alive heartbeats or handshakes with e.g. SIP servers or just between the OLT101and the ONU103to confirm the health of the PON and/or the wireless link113; small numbers of messages such as IGMP queries, i.e. downstream from the OLT101, and IGMP responses, i.e. upstream from the ONU103. These are cases in which the OLT101/ONU103may exercise intelligence in examining the bearer traffic to determine the type of traffic and whether it is merely the first packet in a large stream, or whether it is one of only a very limited number of packets to be exchanged. Another example is the choice to carry POTS calls over the wireless link113rather than awakening the ONU103, based again on intelligence in the OLT101/ONU103that—although there may be a continuing stream of packets to exchange between the OLT101and the ONU103—the packet rate is comfortably within the channel capacity of the wireless link113and does not justify awakening the ONU103and activating its high-speed optical link104.

A method in the OLT101for providing wireless connectivity capability to the ONU103, according to some embodiments will now be described with reference to the flow chart depicted inFIG. 4depicting embodiments of the method for an OLT monitoring process, and with reference toFIG. 5depicting embodiments of the OLT101. The OLT101comprises a Traffic Monitoring Module501, Power Management Module503and Wireless Wake-up Module505. The modules comprised in the OLT101will be described in more detail below. The method comprises the following steps, which steps may as well be carried out in another suitable order than described below.

The Traffic Monitoring Module501monitors downstream traffic from the OLT101to the ONU103. Further, the Traffic Monitoring Module501may also classify the type of incoming downstream traffic, e.g. distinguishing characteristics of bearer traffic such as IPTV or VoIP, and system Control or Management data.

If the incoming downstream traffic is bearer traffic, the Traffic Monitoring Module501in the OLT101determines if there is enough traffic to warrant activating the optical transceiver203in the ONU103. The cases where the incoming downstream traffic is high-priority bearer traffic such as VoIP traffic or Control or Management data will be described in more detail below.

If there is enough downstream traffic, i.e. yes, the method proceeds to step403.

If there is not enough downstream traffic, i.e. no, the method goes back to step401and the OLT101will keep monitoring the downstream traffic. The OLT101may transmit smaller amounts of traffic may to the ONU103using the wireless transceiver201, rather than buffering it.

A Power Management Module503updates the OLT's101record of the power saving mode of the ONU103, i.e. updates the mode from sleep to awake. The OLT101may contain a state table for keeping track of the state of the ONU103. For each ONU103, the state table may have the parameter “sleep” or “awake”. The state table may be stored in a computer readable memory in the OLT101.

This step corresponds to steps304and305inFIG. 3.

If the OLT101determines that the ONU103should be awakened, the wireless wake-up module505in the OLT101may send a wireless wake-up message to the ONU103via the cellular network, i.e. via the wireless link113, to turn on the optical transceiver module203in the ONU103. Thus, the wireless transceiver201in the ONU103receives the wireless wake-up message from the OLT101and is able to awaken upon demand from the OLT101, rather than only upon timer expiration or other local stimulus.

FIG. 6is a combined signaling diagram and flowchart depicting an embodiment of a method for an ONU wake-up sequence through the wireless based wake-up signaling when there is downstream traffic from the OLT101to the ONU103. When the ONU1103is ready to go into sleep mode, it will activate the wireless transceiver201first and then exchange a handshake with the OLT101through wireless connectivity113. The handshake is passed through the base station108. After the handshake, the ONU i103enters the power sleep mode and the OLT101monitors downstream traffic to identify which ONU103may need to be awakened. If there is downstream traffic for the ONU103, the OLT101will first buffer the downstream traffic to the ONU i103and send a wake-up message via the wireline communication link109to the base station108, thence to the ONU103. After turning on the optical transceiver203, the ONU103will synchronize with the OLT101through the PON link104and then power off the wireless transceiver201. Synchronization comprises the process of recovering PON timing on the part of the ONU103, confirming the ability of the ONU103to sustain communications on the optical link104, and possibly adjusting the ONU's103equalization delay on the part of the OLT101. The OLT101will transmit buffered downstream traffic to the ONU103via the optical link104after synchronization is complete. The method comprises the following steps, which steps may as well be carried out in another suitable order than described below.

The ONU1103is ready to go to sleep, i.e. to go into power sleep mode. In some embodiments, the ONU103may make a local decision to go to sleep, or the OLT101may send a message to remind the ONU103to go to sleep.

The ONU1103activates its wireless transceiver201.

The ONU i103, which is ready to go to sleep mode exchanges a handshake with the OLT101via the wireless link113or the optical link104. The purpose of the handshake is to confirm the health of the wireless link113and coordinate the pending transition into sleep mode by the ONU103.

In some embodiments, the OLT101transmits a sleep message to the ONU1103. This step may be unnecessary if the ONU103has been permitted to enter sleep mode as its own local decision.

This step corresponds to step303inFIG. 3.

The ONU103enters sleep mode, in some embodiments after receiving the sleep message from the OLT101in step604,

The OLT101monitors the downstream traffic in the communication network100.

This step corresponds to step402inFIG. 4.

The OLT101identifies that there is downstream traffic to sleeping ONU1103, and analyzes the traffic and determines whether to buffer it, or to forward it over the wireless link113. The OLT101may buffer some bearer traffic until the optical transceiver201in the ONU103is awake. Control or management data and high-priority bearer traffic may be transmitted over the wireless link113.

This step corresponds to step404inFIG. 4.

The OLT101decides that ONU1103should be awakened, i.e. leave sleep mode, and sends a wireless wake-up message to the ONU i103via the base station108.

This step corresponds to step304inFIG. 3.

As mentioned in relation toFIG. 1, the OLT101is connected to the base station108via a wireline communication link109. The OLT101transmits a wireless wake-up message to the ONU1103using the wireline communication link109between the OLT101and the base station108.

This step corresponds to step304inFIG. 3.

The base station forwards the wireless based wake-up message to the ONU1103via the wireless link113.

ONU i103exits out of sleep mode and wakes up, i.e. the optical transceiver203is turned on.

After turning on the optical transceiver, ONU103may synchronize with the OLT101through the optical link104. The purpose of synchronization is to confirm communications capability between OLT101and ONU103, and to adjust the ONU's equalization delay if necessary.

The OLT101transmits the buffered downstream traffic to ONU via the optical link104after it has synchronized with the ONU103in step612.

In some embodiments the wireless transceiver201may be left on even though the traffic is transmitted via the optical link104, and in some embodiments the wireless transceiver201is powered off in that situation. The decision may be dynamic, e.g. based on assessment of the current traffic environment by the OLT101and/or the ONU103, and a prediction of the likelihood of immediately returning to sleep mode or remaining awake for an extended time.

FIG. 7depicts embodiments of a method illustrating an ONU103sleep mode state transition.

This state corresponds to step306inFIG. 3

The ONU103is in the awake mode. In the “Awake” state701, the ONU103is fully responsive, forwarding downstream traffic received on the optical link104and responding to all bandwidth allocations from the OLT101to transmit upstream data via the optical link104.

This step corresponds to step601inFIG. 6.

The ONU103is ready to go to sleep, i.e. to enter sleep mode. The “Go-to-sleep Ready” indication may be obtained internally within the ONU103or externally from e.g. the OLT101:ONU103may make a local decision to go to sleep;OLT101may send a message to remind the ONU103to go to sleep.
Step703

This state corresponds to step603inFIG. 6.

The ONU103activates the wireless transceiver201and exchanges a handshake with the OLT101to confirm the health of the wireless link and the pending transition into sleep mode. In the “Handshake” state703, the ONU optical transceiver201remains on.

This step corresponds to step604inFIG. 6.

After the handshake the OLT101will send the “Sleep” message to place the ONU103into sleep mode. This message is optional. In some embodiments, the ONU103may use handshake completion as a trigger to enter sleep mode without an additional message from the OLT101.

In “Asleep” state, the optical transceiver203is turned off. The ONU103retains wireless connectivity with the OLT101.

Examples of conditions to wake up the ONU103from sleep mode may be:

1. Downstream traffic to the ONU103.

2. Upstream traffic from the ONU103.

The decision to awaken the ONU103may depend on analysis of the traffic type. Both the upstream traffic and the downstream traffic may be of different types, such as for example:a. Bearer traffic that might wake up the ONU103.b. High-priority voice traffic that may be transmitted through wireless connectivity and that does not wake up the ONU103.c. Control or Management data which is transmitted through wireless connectivity and that does not wake up the ONU103.

External stimuli may cause exit from sleep mode earlier than would have been the case if e.g. timer expiration were the only means. External stimuli may comprise, without limitation, control or management data or the arrival of bearer traffic intended to be conveyed in either direction between the OLT101and the ONU103. The possibility that events at the OLT101cause wake-up at the ONU103through the wireless wake-up message is the feature disclosed in the embodiments herein.

High-Priority Bearer Traffic—POTS Call in Energy Saving Mode without Awakening Optical Transceiver

Another example embodiment of the method described inFIG. 3is a POTS call in a power saving mode, which describes a method to deal with high-priority bearer traffic. In a power saving mode due to e.g. AC power failure, the ONU103with wireless connectivity is still able to access the cellular network to provide POTS calls any time.

In this way, the ONU103with wireless connectivity provides longer battery backup time for power shedding mode and provides increased energy saving in sleep mode.

In existing art, when the AC power to the ONU103is down, a power shedding feature may power off the non-essential functions and services of the network100while the optical transceiver203of the ONU103is still on. The network100may comprise an auxiliary source of power, such as a backup battery, which charges while the power grid is in operation, and which provides power to the network units during power outages. Backup battery devices have only a relatively limited amount of energy available before the network units or other device must be shut down. Once the battery has discharged, it is too late to shut down the network units gracefully, and no emergency communications are possible. Some units or devices in the network100are more important than others in terms of the criticality of keeping them powered up during a power outage. Moreover, different devices have different power requirements, which may result in faster than necessary discharge of the auxiliary power source, e.g. the battery. When the AC power is down, the auxiliary power source needs to shed specified loads at specified times and in specified order.

In the embodiments herein, the knowledge at the ONU103of a power failure, or also of a failure or maintenance action on the PON or the optical link104, may be taken as an additional input criterion that allows power shedding and sleep mode to be combined, whereby the optical transceiver203is powered down more aggressively than would have been the case otherwise, and the wireless link113is used for wider purposes than would have been the case otherwise. For example, by activating the wireless transceiver201in the ONU103and then turning off the optical transceiver203, POTS calls are still provided even though the ONU103is in maximum power saving mode. This is illustrated in the flow diagram inFIG. 8.FIG. 8shows AC power failure as an example of a reason for a power saving mode. However; any other reason for power saving mode is also applicable, such as e.g. maintenance, general power saving requirements, fiber cut etc. The method, in the ONU, comprises the following steps, which steps may as well be carried out in another suitable order than described below.

This step corresponds to step301inFIG. 3.

As an example, the AC power to the ONU103fails. The ONU103may continue to operate for a limited amount of time through the availability of a local energy storage device such as a backup battery. Loss of AC power may initiate power shedding. The AC power may be lost for a short or long period of time.

Power saving of non-essential functions of the ONU103is initiated. Power saving of non-essential functions may imply that low-priority/high-volume traffic is discarded in both directions, upstream and downstream. Examples of non-essential functions may be for example high-speed internet access and video service. Both of these imply large volumes of traffic, but are generally low priority, and should be discarded rather than buffered or sent via the wireless link113. As a distinguishing feature from the previous examples, the ONU103may, on the basis of information obtained in step801, abbreviate the intervals or re-prioritize the criteria that it uses to determine its entrance to sleep mode.

The ONU103activates its wireless transceiver201if it is not already active.

This step corresponds to step603inFIG. 6.

The ONU103exchanges handshakes with the OLT101via the wireless link113.

The optical transceiver203in the ONU103is turned off, i.e. the ONU103enters sleep mode. As the wireless transceiver201is activated, step803, wireless link113may handle essential tasks such as POTS calls even though the ONU103is in sleep mode.

Control or Management data may comprise periodic maintenance messages like SIP heartbeat and Internet Group Management Protocol (IGMP) query messages, which may be carried over the wireless link113between the ONU103and application servers, without awakening the ONU103. For IGMP, the IGMP server will periodically send a multicast IGMP query to update its list of active groups. For VoIP service, a heartbeat message is periodically exchanged with the SIP server to keep the session alive. Even the continued health and availability of the wireless link113needs to be occasionally confirmed with a handshake. Such heartbeat exchange messages between ONU103and the OLT101or external application servers may be carried over the wireless link113without awakening the ONU103.

The method described above will now be described seen from the perspective of the ONU103.FIG. 9is a flowchart describing the present method in the ONU103in a communications network100, for providing wireless connectivity capability to the ONU103. As mentioned above the ONU103is being interconnected to an optical line terminal101, referred to as an OLT, via a wireline communications link104and a wireless communications link113. The ONU103is configured to support a sleep mode. The method comprises the further steps to be performed by the ONU103:

This step corresponds to step604inFIG. 6.

The ONU103obtains information about entry into the sleep mode.

The ONU103identifies whether the wireless communications link113is activated or deactivated.

The ONU103activates the wireless communications link113if the wireless communications link113is identified as deactivated.

The ONU103enters sleep mode.

The ONU103provides wireless connectivity capability to the ONU103by means of the wireless communications link113during the sleep mode.

This step corresponds to step304inFIG. 3.

In some embodiments, the ONU103in sleep mode, receives, using the wireless communications link113, control or management data from the OLT101.

This step corresponds to step304inFIG. 3.

In some embodiments, the ONU103in sleep mode transmits, using the wireless communications link113, control or management data or bearer traffic to the OLT101.

This step corresponds to steps609and610inFIG. 6.

In some embodiments, the ONU103, in sleep mode, obtains information via the wireless communications link113from the OLT101about exit out of sleep mode.

In some embodiments, the ONU103exits sleep mode.

In some embodiments, the ONU103receives and transmits, using the wireline communications link104, bearer traffic from and to the OLT101.

To perform the method steps shown inFIG. 9for providing wireless connectivity capability to the ONU103in the communications network100, the ONU103comprises an arrangement as shown inFIG. 10. The ONU103is interconnected to an optical line terminal101, referred to as an OLT, via a wireline communications link104and a wireless communications link113: The ONU103is configured to support a sleep mode.

The ONU103comprises an obtaining unit1001configured to obtain information about entry into the sleep mode. The ONU103further comprises an identifying unit1004configured to identify whether the wireless communications link113is activated or deactivated. The ONU103comprises an activating unit1007which is configured to activate the wireless communications link113if the wireless communications link (113is identified as deactivated. Further, the ONU103comprises an entering unit1009configured to enter sleep mode, and a providing unit1011configured to provide wireless connectivity capability to the ONU103by means of the wireless communications'link113during the sleep mode.

In some embodiments, the obtaining unit1001is further configured to obtain, at the ONU103in sleep mode, information via the wireless communications link113from the OLT101about exit out of sleep mode. In some embodiments, the ONU103further comprising an exiting unit1013configured to exit sleep mode. In some embodiments, the ONU comprises a receiving and transmitting unit1015configured to receive and transmit, using the wireline communications link104, bearer traffic from and to the OLT101. The receiving and transmitting unit1015may further be configured to receive at the ONU103in sleep mode, using the wireless communications link113, control or management data from the OLT101, and to transmit using the wireless communications link113, control or management data or bearer traffic from the ONU103in sleep mode to the OLT101.

The method described above will now be described seen from the perspective of the OLT101, referred to as an OLT, in the communications network100.FIG. 11is a flowchart describing the present method in the OLT101, for providing wireless connectivity capability to the optical network unit103, referred to as an ONU. As mentioned above, the OLT101is interconnected to the ONU103, via a wireline communications link104and a wireless communications link113. The method comprises the further steps to be performed by the OLT101:

When the OLT is in sleep mode, the OLT101identifies bearer traffic to the ONU103.

This step corresponds to step304inFIG. 3.

In some embodiments, the OLT101transmits control or management data to the ONU103via the wireless communications link113, while the ONU103is in sleep mode.

This step corresponds to step304inFIG. 3.

In some embodiments, the OLT101receives control or management data from the ONU103via the wireless communications link113, while the ONU103is in sleep mode.

This step corresponds to step607inFIG. 6.

The OLT101buffers the identified bearer traffic.

The OLT101transmits information about exit out of sleep mode to the ONU103via the wireless communications link113.

The OLT10transmits, after the ONU103has exited sleep mode, the buffered bearer traffic to the ONU103using the wireline communications link104.

The OLT101provides wireless connectivity capability to the ONU103by means of the wireless communications link113during the sleep mode.

To perform the method steps shown inFIG. 11for providing wireless connectivity capability to an optical network unit103, referred to as an ONU, the optical line terminal101, referred to as OLT, in a communications network100comprises an arrangement as shown inFIG. 12. The OLT101is interconnected to the ONU103, via a wireline communications link104and a wireless communications link113. The OLT101comprises an identifying unit1201which is configured to identify bearer traffic to the ONU103when the ONU103is in a sleep mode. Further, the OLT101comprises a buffering unit1204configured to buffer the identified bearer traffic. The OLT101comprises a transmitting unit1207configured to transmit information about exit out of sleep mode to the ONU103via a wireless communications link (113; and configured to transmit, after the ONU103has exited sleep mode, the buffered bearer traffic to the ONU103using the wireline communications link104. In some embodiments, the transmitting unit1207is further configured to transmit control or management data from the OLT101to the ONU103via the wireless communications link113, while the ONU103is in sleep mode. In some embodiments, the OLT101comprises a receiving unit1210configured to receive control or management data from the ONU103via the wireless communications link113, while the ONU103is in sleep mode.

The method described above will now be described seen from the perspective of the communications network100.FIG. 13is a flowchart describing the present method in the communications network100, for providing wireless connectivity capability to an optical network unit103, referred to as an ONU. As mentioned above the communications network100comprises an optical line terminal101, referred to as an OLT. The OLT101and the ONU103is interconnected via a wireline communications link104and a wireless communications link113. The OLT101and the ONU103is configured to support a sleep mode. The method comprises the further steps to be performed by the communications network100:

In some embodiments, the OLT101and the ONU103comprised in the communications network100evaluates characteristics of the bearer traffic.

In some embodiments, the communications network100determines whether to exchange control or management data or bearer traffic over the wireless communications link113or the wireline communications link113based on the evaluated characteristics of the control or management data or bearer traffic.

In some embodiments, the communications network100evaluates failure and congestion of the wireless communications link113and the wireline communications link104.

In some embodiments, the communications network100determines whether to exchange control or management data or bearer traffic over the wireless communications link113or the wireline communications link104based on the evaluated failure and congestion.

This step corresponds to step607inFIG. 6.

In some embodiments, the OLT101and the ONU103buffers the bearer traffic.

In some embodiments, the communications network100obtains information about exit out of sleep mode of the ONU103.

In some embodiments, the communications network100exits the ONU103out of sleep mode.

The communications network100exchanges control or management data or bearer traffic between the OLT101and the ONU103over the wireline communications link104when the ONU103is out of sleep mode

This step corresponds to step304inFIG. 3.

The communications network100exchanges control or management data and bearer traffic between the OLT101and the ONU103over the wireless communications link113when the ONU103is in the sleep mode

The communications network100provides wireless connectivity capability to the ONU103by means of the wireless communications link113during the sleep mode.

The present mechanism for providing wireless connectivity capability to an optical network unit103in a communications network100may be implemented through one or more processors, such as a processing unit1017in the ONU103depicted inFIG. 10and a processing unit1215in the OLT101depicted inFIG. 12, together with computer program code for performing the functions of the embodiments herein. The processor may be for example a Digital Signal Processor (DSP), Application Specific Integrated Circuit (ASIC) processor, Field-programmable gate array (FPGA) processor or micro processor. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the ONU103and/or OLT101. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the ONU103and/or OTL101remotely.

In summary, when there is downstream traffic of sufficient priority or volume destined for the sleeping ONU103, the OLT101will send a wireless wake-up message through the base station108to the ONU103to turn on the optical transceiver203to receive the buffered downstream traffic. When there is no downstream traffic, or low-volume or low-priority traffic only, the ONU103may be permitted to remain asleep indefinitely. In this way, the ONU103with wireless connectivity provides an adaptive wake-up mechanism for additional power saving.

In a power saving mode due to AC power failure, an ONU103with wireless connectivity may still access the cellular network to provide POTS calls at any time, without awakening the ONU103. This way, the ONU103with wireless connectivity provides longer battery backup life for power shedding and conserves more energy during sleep mode.

Even though the optical transceiver203of the ONU103is asleep, heartbeat messages may reach the VoIP SIP server to keep a connection active through the wireless connection113. For IGMP, the IGMP server will periodically send a multicast IGMP query to update its list of active groups, which may be conveyed over the wireless link113without awakening the ONU.

The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the embodiments, which is defined by the appended claims.

It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components, but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. It should also be noted that the words “a” or “an” preceding an element do not exclude the presence of a plurality of such elements.

It should also be emphasized that the steps of the methods defined in the appended claims may, without departing from the embodiments herein, be performed in another order than the order in which they appear in the claims.