WO2017151026A1

WO2017151026A1 - Node, device and methods for managing wireless communication over multiple channels

Info

Publication number: WO2017151026A1
Application number: PCT/SE2016/050175
Authority: WO
Inventors: Parth AMIN; Andreas HÖGLUND
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-03-04
Filing date: 2016-03-04
Publication date: 2017-09-08

Abstract

The present invention relates to a node (44; 64) for enabling communication with at least one device (41-43; 61-63) over multiple channels (c1-c3; c1-c6) in a wireless communication network (40; 60), wherein each channel occupies a frequency range and at least one frequency range belongs to an unlicensed spectrum. The node (44; 64) is configured to obtain a channel switch schedule (70), wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node (44; 64) to communicate with the at least one device (41-43; 61-63); and configured to transmit the channel switch schedule (70) to the at least one device (41-43; 61-63). The invention also relates to a method for enabling communication between a node and at least one device; a device (41-43; 61-63) adapted to communicate with a node; and a method for enabling communication between a device and a node.

Description

NODE, DEVICE AND METHODS FOR MANAGING WIRELESS

COM MUNICATION OVER MULTIPLE CHANNELS

TECHNICAL FIELD

The present invention relates to a node and a method for enabling communication in a wireless communication network. The present invention also relates to a device adapted to communicate with a node and a method for enabling communication between a device and a node.

BACKGROUND

Emerging radio access technologies for Internet of Things (loT) are being developed to address the ever emerging market needs and use cases, which includes IEEE 802.11ah,

Sigfox, LoRa, 3GPP LTE machine type communications, 3GPP LTE narrowband loT, Bluetooth long range, Bluetooth mesh. Some of these technologies such as IEEE 802.11ah, Sigfox, LoRa are planned to be deployed in the unlicensed spectrum at sub 1 GHz. Also, cellular technologies such as 3GPP LTE are typically deployed in the licensed spectrum, but work is ongoing to develop LTE-Licensed Assisted Access (LTE-LAA) and LTE-Unlicensed (LTE-U), which may also be deployed in the unlicensed spectrum.

It is expected that 802.11ah will be deployed in 863 MHz to 868.6 MHz bands in EU, 916.5 MHz to 927.5 MHz in Japan and 917.5 MHz to 923.5 MHz in South Korea [2]. Also LoRa and Sigfox is being deployed in 868 MHz band in EU. EU regulation on spectrum usage in 863 - 868 MHz usage allows the maximum duty cycle of 2.8%, the duty cycle being the percentage of active signal in the system per time period, for SRDs supporting Listen before talk (LBT) and Adaptive Frequency Agility (AFA) [2]. Also, EU and Japan limits the channel bandwidths that can be used i.e. either 1 MHz or 2 MHz channels are available in EU 863 - 868 MHz or 1 MHz channels in Japan 916 - 927 MHz spectrum. For the unlicensed spectrum, both the access point (AP) and the station (STA) needs to fulfil the same duty cycle limitation i.e. even though the AP serves a number of stations, such as sensors, it is not allowed to use a higher duty cycle compared to the stations. In case 802.11ah is qualified as short range devices (SRD) supporting LBT and AFA, AP and STA transmissions has to be within 2.8% duty cycle. Duty cycle of 2.8% corresponds to 100 sec of transmission / hour.

802.11ah AP has to adhere to the duty cycle requirements while periodically broadcasting beacon transmissions to the STAs and also transmitting unicast transmissions to the served STAs.

802.11ah AP transmits full beacon every Target Beacon Transmission Time (TBTT) intervals and shorter beacons more frequently every Target Short Beacon Transmission Time (TSBTT) intervals. Typically the size of the full and short beacons are around 100 and 20 bytes respectively!!].

For TBTT interval of 1 sec and TSBTT interval of 100 msec, 802.11ah AP in TIM mode, consumes 1.92% of duty cycle for beacons transmissions, based on channel bandwidth of 1 MHz and modulation and coding scheme 10, MCSIO. Due to large overhead of beacons, only 0.88% of duty cycle is left for actual packet transmissions, which corresponds to 150 bytes of packet transmissions per second in DL.

Similarly, using 2 MHz of channel bandwidth and MCS0, AP consumes 0.55% of duty cycle for beacon transmissions. Duty cycle left for actual packet transmissions corresponds to 1530 bytes of packet transmissions per second in DL.

WO 2013/174928, by Ecole Polytechnique Federal De Lausanne (EPFL) [6], proposes a method of limiting the duty cycle within limits of the geographical region by calculating time required to transmit and comparing it with time of total transmission in the past hour and maximum allowed transmissions in the past hour.

Since the duty cycle limitations is per channel, switching to a new channel gives a new duty cycle that may be used for transmission. 802.11 defines channel switch announcements (CSA), which enables an AP to announce that it is switching to a new channel before it begins transmitting on that channel [3]. This allows STAs that support CSA to transition to the new channel with minimal downtime. The number of channel switch announcements that have to be sent prior to switching to a new channel is defined, and the default CSA count is four announcements. The channel switch announcement element is part of beacons or probe responses send by the AP.

Figure 1 illustrates a CSA element format 10 defined in reference [3]. It comprises Element ID 11, Length 12, Channel switch mode 13, New channel number 14 and Channel switch count 15, each having a bit length of 1 octet.

The AP sends several beacons to indicate the change of primary channel to the served STAs, before moving to another channel. As indicated in WO 2014/068456 Al, by Renesas Mobile Corporation [4], the AP may announce a list of channels in which AP may switch along with their priorities from the present primary channel. Problem of unreachability of the STA in downlink based on 802.11ah is relevant, as the STA sleeps most of the time, making it likely that it may miss multiple CSA announcements made by the AP. This will result in a problem where the AP has moved to a different primary channel, whereas the STA is still on the old primary channel. One of the solutions to the problem is addressed in US 2014/0016568 Al, by Renesas Mobile Corporation [5], where the AP also sends post announcements of channel switch on the old channel, although data transmission has moved to a new channel.

For LTE-U addressing machine type communication (MTC) it is reasonable to consider the same bands as for 802.11ah, SigFox, and LoRa above. Therefore LTE-U would have to obey the same regulations and would face the same problems in terms of duty cycles, especially for the evolved Node B, eNB, transmissions.

SUMMARY

An object with the present invention is to provide a more efficient use of spectrum resources having constraint on duty cycle, e.g. the unlicensed spectrum, compared to prior art solutions. The object is achieved by a node for enabling communication with at least one device over multiple channels in a wireless communication network. Each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum. The node is configured to obtain a channel switch schedule, wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the at least one device; and to transmit the channel switch schedule to the at least one device.

The object is also achieved by a method for enabling communication between a node and at least one device over multiple channels in a wireless communication network. Each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum. The method comprises obtaining a channel switch schedule, wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the at least one device; and transmitting the channel switch schedule to said at least one device.

The object is further achieved by a device adapted to communicate with a node over multiple channels in a wireless communication network. Each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum The device is configured to acquire a channel switch schedule from the node, wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the device; and move across multiple channels based on the acquired channel switch schedule.. The object is also achieved by a method for enabling communication between a device and a node over multiple channels in a wireless communication network. Each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum. The method comprises acquiring a channel switch schedule from the node, wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the device; and moving across multiple channels based on the acquired channel switch schedule. An advantage is that a larger portion of the available transmission time, which is restricted as a result of the limited duty cycle requirement in unlicensed spectrum, can be used for communication between the node and the device.

Another advantage is faster transition between different serving channels compared to where an access point sends channel switch announcements several times before moving to a new serving channel. Another advantage is a reduction in beacon signalling overhead by using a single beacon compared to using several for each channel switch in the prior art.

An advantage when using a broadcast transmission to transmit a channel switch schedule is that serving channels are pre-planned and distributed in time by node (e.g. AP), and the information is shared with all devices using the broadcast transmission, thereby solving the problem of unreachable devices (e.g. STA) in downlink.

The method further may allow for offloading of narrow licensed band-widths, available e.g. sub 1 GHz. The method may also be able to consider both uplink and downlink traffic when estimating (e.g. calculating) the need of the channel switch at the node. Further objects and advantages may be obtained from the detailed description by a skilled person in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a prior art channel switch announcement element format defined in 802.11.

Fig. 2 illustrates an example of a channel switch announcement element format for announcing a channel switch schedule that may be used in the method described in figure 3 and 7.

Fig. 3 illustrates a method for enabling communication between a node and at least one device over multiple channels.

Fig. 4 illustrates an example of broadcast transmission of the channel switch schedule from node to devices.

Figs. 5a-5c illustrate different serving channels at different times.

Figs. 6a-6c illustrate different serving channels for each device at different times.

Fig. 7 is a schematic illustration of a channel switch schedule with an anchor channel.

Fig. 8 illustrates a method for enabling communication between a device and a node over multiple channels. Fig. 9 illustrates a node configured to perform the method described in figure 3. Fig. 10 illustrates a device configured to perform the method described in figure 7. DETAILED DESCRIPTION

The existing technology used today experience certain limitations that has to be addressed in order to provide a wireless environment that may be used for loT. The present disclosure will enable the node, e.g. AP, eNB or CN (core network) node, to limit duty cycle usage to the required regulations and still cater the needs for serving the devices, e.g. STAs, UEs or terminals, in the wireless communication networks. Furthermore, DL operation and broadcast of pilots etc. in LTE-U operation can be achieved if regulatory duty cycles must be met.

The limited duty cycle requirement, e.g. deployed in EU / Japan in the sub 1 GHz unlicensed spectrum, is sufficient for communication purposes between a node (AP/eNB/CN-node) and one or more devices (STAs/UEs) when enabling dynamic transmissions using a channel switch schedule (i.e. transmissions on different serving channels for pre-defined serving time durations), which may include both unlicensed spectrum and licensed spectrum. The node obtains the allowed transmission time (e.g. computes the allowed transmission time or requests the allowed transmission time from an external source) for each channel based on the duty cycle requirement of the deployed geographical region. The allowed

transmission time may also be based on recorded load for various channels, the operator's available licensed bands, QoS requirements of the served devices, etc.

Based on the obtained or calculated allowed transmission time a channel switch schedule is obtained, i.e. provided from an external source or the node computes a channel switch schedule, which may be a schedule of both licensed and unlicensed serving channels and the corresponding serving time durations which the node plan to serve the devices on these channels. The channel switch schedule may be periodic and may also be pre-defined.

The node may transmit the channel switch schedule to one or more devices as a part of a broadcast transmission, e.g. as part of a beacon or system information broadcast (SIB), or as a part of probe responses or vendor specific messages or other control or data

transmissions between the node and each device. Thereby, all the devices are notified of a series of channel switch announcements comprising information regarding serving channels that the node plan to use in the defined durations/periodicity. Since the channel switch schedule is carried out over a rather long time, devices waking up from sleep/DRX would instantaneously know which band to use (as long as system or beacon information is still valid).

Figure 2 illustrates an example of a modified channel switch announcement element format 20 for announcing a channel switch schedule that may be used in the method described in figure 3 and 7. The three first parts: Element ID 11, Length 12 and Channel switch mode 13 are identical to the prior art channel switch announcement element format 10 illustrated in figure 1. However, last two parts (i.e. new channel number 14 and channel switch count 15) are substituted by Channel switch schedule 21 having a length of n octets, which depends on the size of the channel switch schedule contained therein.

In this example, the channel switch schedule 21 comprises six portions 22. Every other is a channel number portion cl, c2 and c3, respectively, and every other is a time portion tl, t2 and t3, respectively. Each channel number portion has a length of m bits and every time portion has a length of p bits. As an example: n=3, m=3 and p=5, which means that the channel switch schedule 21 contains 24 bits.

In figure 3, a flowchart illustrating a method for enabling communication between a node and at least one device over multiple channels in a wireless communication network is disclosed. Each channel occupy a predetermined, or adaptable, frequency range and at least one frequency range belongs to an unlicensed spectrum. However at least one frequency range may also belong to a licensed spectrum.

Unlicensed spectrum has a number of restrictions on the usage, based on the frequency spectrum (e.g. sub 1 GHz, 2.4 GHz, 5 GHz etc.) and corresponding geography (e.g. US, Europe, Japan), which varies by the following factors:

1. Duty cycle restrictions

2. Frequency hopping (e.g. Bluetooth uses this in 2.4 GHz)

3. Listen before talk (e.g. Wifi uses this in 2.4 GHz)

4. Power of transmitter That being said, transmitter operating in the unlicensed spectrum has to adhere one or more regulations for the corresponding frequency spectrum and geography, such as e.g. duty cycle below 2.4%, frequency hopping for the specific time period, listen before talk, limit the transmit power below "x" dB. The method shown in figure 3 is performed in a node (e.g. AP/eNB/CN-node) and starts in step 30, and in step 31, the node investigates if a channel switch schedule is available within the wireless communication network, e.g. from another node in the network. If the channel switch schedule is available, then the flow continues to step 36. However, if the channel switch schedule is not available, the flow continues to step 32a. The channel switch schedule indicates a list of serving channels and corresponding serving time durations, as illustrated in connection with figure 2, for use by the node to

communicate with the at least one device.

In step 32a, information of allowed duty cycle for each channel belonging to the unlicensed spectrum is obtained , e.g. based on spectrum regulations of the geography e.g. ETSI requirements for EL⁾, FCC for US, ARIB for Japan etc. The information of the allowed duty cycle for each channel belonging to the unlicensed spectrum may comprise a maximum transmission per a given time period, e.g. EU regulation on spectrum usage in 863 - 868 MHz usage allows the maximum duty cycle of 2.8% for SRDs supporting Listen before talk (LBT) and Adaptive Frequency Agility (AFA). Duty cycle of 2.8% corresponds to 100 sec of transmission / hour for a specific transmitter (Access point and served MTC devices in our case), and if this is the case the flow continues to step 32b, in which a number of allowed transmissions per given time period for each channel belonging to the unlicensed spectrum may be determined based on the allowed duty cycle for each channel belonging to the unlicensed spectrum (obtained in step 32a) before the flow continues to step 33. A decision is made in step 33 to include UL/DL traffic for the node, and if UL/DL traffic for the node is decided to be included, the flow continues to step 34a, in which UL/DL traffic for the node is estimated.

On the other hand if UL/DL traffic for the node is not included, then the flow continues from step 33 directly to step 35 in which the allowed transmission time for each channel is based on the information of allowed duty cycle for each channel belonging to the unlicensed spectrum, and optionally the allowed transmission time for each channel may be further based on the determined number of allowed transmissions per given time period if step 32b is performed. If the information of the allowed duty cycle for each channel belonging to the unlicensed spectrum comprises a maximum transmission per a given time period, then the flow continues from step 34a to step 34b, in which required transmission time in uplink/downlink per given time period is determined based on the estimated uplink /downlink traffic for the node. The flow thereafter continues to step 35, in which the step of obtaining allowed transmission time for each channel is further based on the estimated uplink/downlink traffic, and optionally the allowed transmission time for each channel may be further based on the determined required transmission time in uplink/downlink per given time period.

When the allowed transmission time for each channel is obtained, based on different aspects as explained more in detail below, the flow continues to step 36, wherein the channel switch schedule is obtained either from within the wireless communication network (if available, see step 31) or based on the allowed transmission time for each channel obtained in step 35. The channel switch schedule may further comprise at least one anchor channel, described in more detail in connection with figure 7.

The flow continues to step 37, in which the channel switch schedule is transmitted to the at least one device. The channel switch schedule may be transmitted as part of a broadcast transmission, and the broadcast transmission may comprise beacon information or system information. The channel switch schedule may be a periodic schedule, as illustrated in connection with figures 6a-6c. If at least one anchor channel is used, the channel switch schedule may be transmitted to the at least one device over the at least one anchor channel.

A node (e.g. AP/eNB/CN-node) for enabling communication with at least one device over multiple channels in a wireless communication network may be configured to perform the method described in connection with figure 3. Each channel occupy a predetermined, or adaptable, frequency range and at least one frequency range belongs to an unlicensed spectrum. However at least one frequency range may also belong to a licensed spectrum. The node is configured to: obtain a channel switch schedule, wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the at least one device, and transmit the channel switch schedule to the at least one device.

The channel switch schedule may be available within the wireless communication network and can be retrieved e.g. from another node in the network, or may be computed within the node.

The node may be configured to transmit the channel switch schedule as part of a broadcast transmission, and the broadcast transmission may comprise beacon information or system information. The channel switch schedule may be a periodic schedule, as illustrated in connection with figures 6a-6c.

If the channel switch schedule is not available within the wireless communication network, the node may be configured to: obtain information of allowed duty cycle for each channel belonging to the unlicensed spectrum, and obtain allowed transmission time for each channel based on the information of allowed duty cycle for each channel belonging to the unlicensed spectrum, wherein the channel switch schedule may be obtained, e.g. calculated by the node, based on the allowed transmission time for each channel.

The information of the allowed duty cycle for each channel belonging to the unlicensed spectrum may comprise a maximum transmission per a given time period, as explained above. If this is the case, the node may be further configured to: determine a number of allowed transmissions per given time period for each channel belonging to the unlicensed spectrum based on the allowed duty cycle for each channel belonging to the unlicensed spectrum, wherein the allowed transmission time for each channel is further based on the determined number of allowed transmissions per given time period.

Optionally, the node may be further configured to estimate uplink /downlink traffic for the node, wherein the allowed transmission time for each channel is further obtained based on the estimated uplink/downlink traffic. If the unlicensed spectrum comprise a maximum transmission per a given time period, then the node may be further configured to: determine required transmission time in uplink/downlink per given time period based on the estimated uplink /downlink traffic for the node, wherein the allowed transmission time for each channel is further based on the determined required transmission time in uplink/downlink per given time period.

The channel switch schedule may comprise at least one anchor channel, as described in connection with figure 7, and in that case the node may be further configured to transmit the channel switch schedule to the at least one device over the at least one anchor channel. The anchor channel may for example belong to the licensed spectrum. Figure 4 illustrates an example of broadcast transmission of the channel switch schedule from a node 44 to at least one device, in this example three devices 41-43, in a wireless communication network 40. The node 44 obtains the channel switch schedule, as described in connection with figure 3, and transmits the channel switch schedule to the devices 41-43, e.g. by using a broadcast transmission. In this example, the node (AP/eNB/CN-node) 44 transmits the following information to the three devices (STAs/UEs) 41-43 along with other information, such as beacon transmission or SIB in LTE:

Serving channel cl (unlicensed spectrum) at time tl

Serving channel c2 (licensed spectrum) at time t2

- Serving channel c3 (unlicensed spectrum) at time t3

Figures 5a-5c illustrate different serving channels at different times, and shows the impact of the transmission of the channel switch schedule illustrated in figure 4. This results in that the node serves the devices on a single channel (cl, c2 or c3) at a particular point in time and moves across different channels at different time instances.

Figure 5a illustrates the situation at t=tl when the node serves the devices over channel cl, figure 5b illustrates the situation at t=t2 when the node serves the devices over channel c2, and figure 5c illustrates the situation at t=t3 when the node serves the devices over channel c3.

Figures 6a-6c illustrate a wireless communication network 60 using different serving channels for each device at different times, and shows how a node 64 serves at least one device, in this example three devices 61-63, on multiple channels at each time instant and moves periodically across different channels.

In this example, the node 64 has transmitted the following information to each of the three devices 61-63, using dedicated signalling and not broadcasting as previously described in connection with figure 4, together with instructions that the channel switch schedule is a periodic schedule:

For device 1

Serving channel cl (unlicensed spectrum) at time tl

Serving channel c4 (unlicensed spectrum) at time t2

For device 2

Serving channel c2 (unlicensed spectrum) at time tl

Serving channel c5 (unlicensed spectrum) at time t2

For device 3

Serving channel c3 (unlicensed spectrum) at time tl

Serving channel c6 (unlicensed spectrum) at time t2

Figure 6a illustrates the situation at t=tl when the node 64 serves the first device 61 over channel cl, the second device 62 over channel c2 and the third device 63 over channel c3.

Figure 6b illustrates the situation at t=t2 when the node 64 serves the first device 61 over channel c3, the second device 62 over channel c2 and the third device 63 over channel c3. Figure 6c illustrates the situation at t=t3 when the node 64 again serves the first device 61 over channel cl, the second device 62 over channel c2 and the third device 63 over channel c3, as illustrated in figure 6a. This will be repeated until a new channel switch schedule has been provided by the node 64. Figure 7 is a schematic illustration of a channel switch schedule 70 with an anchor channel 71. In this example twelve channels are available for use by the node to serve one or more devices. One channel is assigned to be an anchor channel 71, and five channels below the anchor channel 71 are designated 72 and six channels above the anchor channel 71 is designated 73. It should be pointed out that the channels does not have to be situated within the same frequency range, and some channels may be situated in a sub GHz range, and some channels may be situated in the 2GHz range.

In one embodiment system information (SI) would always be broadcasted on an anchor licensed channel 71 and unlicensed channels 72 are used for offloading, as illustrated in Figure 7. A channel in the unlicensed spectrum could be used as an unlicensed anchor channel or instead of transmitting the channel switch schedule by broadcasting, pre-defined transmissions of the channel switch schedule over multiple channels may be performed, not shown). In another embodiment the Channel Switch Schedule would be a guidance to UEs and the presence of e.g. pilot signals (CRS, PSS/SSS, etc.) could indicate if a specific channel is currently allowed to be used by STAs/UEs, e.g. for off-loading. In yet another

embodiment, only channels in the unlicensed spectrum are considered and an unlicensed anchor channel is specified in the Channel Switch Schedule for fall-back in case the current channel cannot be used.

In the example illustrated in figure 7, channels 72 occupy a frequency range belonging to the unlicensed spectrum and channels 73 occupy a frequency range belonging to a unlicensed or licensed spectrum. The anchor channel 71 may belong to either unlicensed or licensed spectrum. The shaded parts 74 of the channels illustrate the intended use of the respective channel as serving channel for a specified time duration, and the channel switch schedule 70 that may be transmitted on the anchor channel 71 using broadcast transmission is: c3,tl: cl,t2; c8,t3; c9, t4; cll,t5; c4,t6. Fig. 8 illustrates a method for enabling communication between a device and a node over multiple channels.

In figure 8, a flowchart illustrating a method for enabling communication between a device and a node over multiple channels in a wireless communication network is disclosed. Each channel occupy a predetermined, or adaptable, frequency range and at least one frequency range belongs to an unlicensed spectrum. However at least one frequency range may also belong to a licensed spectrum.

The method is performed in a device (STA/UE) and starts in step 80, and in step 81, the device acquire a channel switch schedule from the node, wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the device.

The channel switch schedule may be acquired as part of a broadcast transmission, and the broadcast transmission may comprise beacon information or system information. The channel switch schedule may be a periodic schedule, as illustrated in connection with figures 6a-6c. The channel switch schedule may comprise at least one anchor channel, and if at least one anchor channel is used, the channel switch schedule may be acquired over the at least one device over the at least one anchor channel.

Furthermore, if the channel switch schedule comprises at least one anchor channel, step 82 may include using the at least one anchor channel as fall-back in case the serving channel cannot be used.

The flow continues to step 82, in which the device obeys the instructions received from the node and move across multiple channels based on the acquired channel switch schedule.

While moving (switching/transiting/shifting) across multiple channels based on the acquired channel switch schedule, the device may assist the node to estimate traffic in the network, and in step 83 a decision is made to assist the node. If decided to assist the node, the flow continues to step 84, in which the uplink traffic for the device is estimated, and in the following step 85, the node is informed of the estimated uplink traffic for the device. When the node has been informed in step 85, or it is decided in step 83 not to estimate traffic in the network and assist the node, the flow continues to step 86 and waits for a decision to update the channel switch schedule or not. The flow is fed back to step 81 if an update is required, or the flow ends in 87 if no update of the channel switch schedule will be provided.

A device (e.g. STA/UE) adapted to communicate with a node over multiple channels in a wireless communication network may be configured to perform the method described in connection with figure 8. Each channel occupy a predetermined, or adaptable, frequency range and at least one frequency range belongs to an unlicensed spectrum. However at least one frequency range may also belong to a licensed spectrum.

The device is configured to: acquire (e.g. receive) a channel switch schedule from the node, wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the device, and - move across multiple channels based on the acquired channel switch schedule.

The channel switch schedule may be acquired as part of a broadcast transmission, and the broadcast transmission may comprise beacon information or system information. The channel switch schedule may be a periodic schedule, as illustrated in connection with figures 6a-6c. The channel switch schedule may comprise at least one anchor channel, and if at least one anchor channel is used, the device may be further configured to acquire the channel switch schedule over the at least one anchor channel.

Furthermore, if the channel switch schedule comprises at least one anchor channel, the device may further be configured to use the at least one anchor channel as fall-back in case the serving channel cannot be used. The device may further be configured to: estimate uplink and/or downlink traffic for the device, and inform the node of the estimated uplink and/or downlink traffic. Figure 9 illustrates a node 90 for enabling communication with at least one device over multiple channels in a wireless communication network, each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum.

However at least one frequency range may also belong to a licensed spectrum. The node 90 comprises: a first module 91 configured to obtain a channel switch schedule (which may be a periodic schedule), wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the at least one device, and - a second module 92 transmit the channel switch schedule to the at least one device.

The second module 92 may be configured to transmit the channel switch schedule as part of a broadcast transmission, and the broadcast transmission may comprise beacon information or system information.

The first module 91 may obtain information regarding the channel switch schedule from within the wireless communication network (if available) or obtain the channel switch schedule within the node using: a third module 93 configured to obtain information of allowed duty cycle for each channel belonging to the unlicensed spectrum, a fourth module 94 configured to obtain allowed transmission time for each channel based on the information of allowed duty cycle for each channel belonging to the unlicensed spectrum. The channel switch schedule may be obtained based on the allowed transmission time for each channel. an optional fifth module 95 configured to, when the information of the allowed duty cycle for each channel belonging to the unlicensed spectrum comprises a maximum transmission per a given time period, determine a number of allowed transmissions per given time period for each channel belonging to the unlicensed spectrum based on the allowed duty cycle for each channel belonging to the unlicensed spectrum. The allowed transmission time for each channel may further be based on the determined number of allowed transmissions per given time period. an optional sixth module 96 configured to estimate uplink /downlink traffic for the node. The allowed transmission time for each channel may further be obtained based on the estimated uplink/downlink traffic. an optionally seventh module configured to, when the information of the allowed duty cycle for each channel belonging to the unlicensed spectrum comprises a maximum transmission per a given time period, determine required transmission time in

uplink/downlink per given time period based on the estimated uplink /downlink traffic for the node. The allowed transmission time for each channel may further be based on the determined required transmission time in uplink/downlink per given time period.

Fig. 10 illustrates a device 100 adapted to communicate with a node over multiple channels in a wireless communication network, each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum.

The device 100 comprises: a first module 101 configured to acquire a channel switch schedule from the node, wherein the channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the device, a second module 102 configured to move across multiple channels based on the acquired channel switch schedule, an optional third module 103 configured to estimate uplink and/or download traffic for the device, and an optional fourth module 104 configured to inform the node of the estimated uplink and/or downlink traffic.

The channel switch schedule may comprise at least one anchor channel, and the first module 101 may be configured to acquire the channel switch schedule from the node over the at least one anchor channel. When channel switch schedule comprises at least one anchor channel, the second module 102 may further be configured to use the at least one anchor channel as fall-back in case the serving channel cannot be used.

As described above, in case the channel switch schedule is not available within the network, the AP computes the allowed transmission time (Tc) for each channel (c), based on the duty cycle requirement of the unlicensed spectrum in the deployed geographical region. Of the total allowed transmission time, the AP uses the time for both beacon transmissions and packet transmission to the served STA. The AP may select the number of STAs it can serve, based on the needed data rate requirements per STAs in the use case. Transmissions on channels in both unlicensed and licensed spectrum may be considered.

Further, the AP computes the channel switch schedule, which is an ordered list of serving channels c and corresponding time durations (e.g. starting time of transmission, duration of transmission and/or ending time of transmission) for which the node plan to serve on that channel. As mentioned above, the channel switch schedule can be periodically repeated until updated by the AP, i.e. the channel switch schedule may be valid for a longer period of time until updated by a new one.

The AP may transmit the channel switch schedule as a part of beacon information to the served STAs, for instance using a modified channel switch announcement (as exemplified in connection with figure 2). The modified CSA may be seen as a series of prior art CSAs.

Beacon transmission comprising the channel switch schedule may be repeated for one or more times. Thereby, all the STAs are aware of series of channel switch announcements (CSA) that the AP plan to perform in the defined duration.

The above is equally applicable to LTE-U where AP is replaced by eNB, STA is replaced by UE and beacon is replaced by system information (SI). The channel switch schedule could then be communicated to the UEs in the cell in form of a new system information block (SIB). The channel switch schedule would indicate in which channel the system is currently located including synchronisation signals SSS/PSS, system information broadcast, cell reference symbols (CRS), PRACH, PUCCH/(E-)PDCCH control channel transmissions, etc. This would be applicable to e.g. LTE-U, eMTC and NB-loT. In the NB-loT case the entire system bandwidth of 200 kHz would change, whereas in eMTC the central 6 PRBs may be shifted and PUSCH and PDSCH could still be scheduled in any channel. As long as SI has not been updated, the UE can rely on the stored channel switch schedule for example when waking up for DRX to monitor paging or upon data transmission.

Regional regulations for unlicensed frequency ranges often specify two alternatives for transmitters to fulfil, either a low-duty cycle should be met or a higher duty-cycle should be met under the condition that the transmitter applies e.g. listen-before-talk carrier sensing (LBT) and adaptive frequency agility (AFA). Optionally the channel switch schedule may include info to the STAs/UEs regarding which alternative that should be obeyed and it would therefore be possible to dynamically switch between the two alternatives.

In eMTC and NB-loT embodiments the channel switch schedule may be carried out with a granularity of the BCCH modification period.

The invention would not necessarily be limited to fulfilling the duty-cycle regulations, if AFA regulations can be addressed on a time scale longer than the BCCH modification period, the eNB/AP could dynamically update the channel switch schedule to fulfil AFA regulations.

In the current description, the term "node" refers to any node within a wireless

communication network, such as an access point (AP), evolved node B (eNB) or core network (CN) node. The term "device" could refer to a wireless device. It could also refer to a mobile or stationary device or machine. It could for example refer to a station (STA) , a terminal or a user equipment (UE).

The "licensed spectrum" is the part of the radio frequency spectrum that is specifically used for certain types of transmissions and requires a license to use. The licensed spectrum is usually made up of certain frequency ranges or bands, such as between 700 MHz and 2.6 GHz in the U.S., and are typically jurisdiction specific. Transmissions such as cellular communication (e.g. for Long term evolution, LTE) typically occurs in the licensed spectrum. Up to now, the spectrum used by LTE is dedicated to LTE. This has the advantage that LTE system does not need to care about the coexistence issue and the spectrum efficiency can be maximized. However, the spectrum allocated to LTE is limited which cannot meet the ever increasing demand for larger throughput from applications/services. Therefore, discussions are ongoing in 3GPP to initiate a new study item on extending LTE to exploit unlicensed spectrum in addition to licensed spectrum. In view of the current invention, the term licensed spectrum is used to describe a frequency spectrum that does not have a duty cycle requirement and/or need to use Listen-Befo re-Talk when transmitting.

The term "unlicensed spectrum" refers to the part of the radio frequency spectrum in a given jurisdiction that does not require a license to transmit on it. For example, the 3GPP initiative "License Assisted Access" (LAA) aims to allow LTE equipment to operate in an unlicensed 5 GHz radio spectrum. The unlicensed 5 GHz spectrum is used as an extension to the licensed spectrum. Regulatory requirements, however, may not permit transmissions in the unlicensed spectrum without prior channel sensing. Since the unlicensed spectrum must be shared with other radios of similar or dissimilar wireless technologies, a so called Listen- Before-Talk (LBT) method needs to be applied. Prior to occupying a channel in an unlicensed band, the network needs to check the availability of the channel by means of LBT. When the network has already accessed a channel, it may, in the following and adjacent transmission time interval, start transmission immediately, e.g. from symbol 0, without performing LBT. Today, the unlicensed 5 GHz spectrum is mainly used by communication terminals implementing the IEEE 802.11 Wireless Local Area Network (WLAN) standard. This standard is known under its marketing brand "Wi-Fi." The unlicensed spectrum is typically distributed at sub 1 GHz and above 2.4 GHz and has a few characteristics that differ from licensed bands. For example it has the duty cycle requirements. Further, it usually needs to apply LBT, and thus an unlicensed channel could be seen as a channel having a duty cycle requirement and/or which needs to apply LBT for transmissions.

The frequency spectrum comprises: unlicensed spectrum and licensed spectrum. The unlicensed spectrum comprises at least one frequency range, (also known as unlicensed frequency band); and the licensed spectrum comprises at least one frequency range (also known as licensed frequency band). Each unlicensed frequency band and licensed frequency band comprises one or more channels adapted for communication between a node and a device. An "anchor" channel is a channel that is used as a fallback channel if the scheduled channel is unavailable, or as a dedicated channel on with the channel switch schedule is communicated to the devices using broadcast transmission.

With "uplink/downlink traffic for the node" we refer to any type of data communication between a node and devices configured to communicate with the node. A duty cycle is a regional restriction of transmission time per time period for a specific channel. The duty cycle could be given in percent (%), which is the amount of allowed transmission for a predetermined time period. Typically, the unlicensed spectrum has duty cycle requirements/restrictions on transmission whereas the licensed spectrum does not.

A channel switch schedule is typically a list of channels to use for a given time period, and comprises a list of serving channels and the corresponding serving time durations for each channel, to be used, either for a predetermined time period or until a new channel switch schedule is provided by the node.

When there is a channel present belonging to the licensed frequency spectrum there is no limitation in the duty cycle, but there might be other problems with capacity in the channels belonging to the licensed spectrum. This situation will benefit from the invention in that the licensed channels are off-loaded to channels in the unlicensed spectrum.

Since there is no duty cycle limitations for channels belonging to the licensed frequency spectrum it, the need for channel switching for the licensed bands used is based on other parameters than duty cycle. Thus, the licensed spectrum is not limited by the duty cycle, but is limited by the capacity in the transmission channels, i.e. the factor of transmission bandwidth of the channels and signal to noise ratio of the users connected to the node. Based on the estimates of the uplink and downlink traffic of the users, transmission bandwidth and signal to noise ratio of the user, the node decides to serve one set of users using the licensed spectrum and the rest of the users may be offloaded to the unlicensed spectrum. Also lower cost of the unlicensed spectrum and higher quality of service with the licensed spectrum has to be considered while offloading the users from the licensed to unlicensed spectrum.

Abbreviations AFA Adaptive Frequency Agility

AP Access point

BCCH Broadcast Control Channel

BSS Basic Service Set

CN Core Network

CRS Cell Reference Symbols

CSA Channel Switch Announcements

DL Downlink

DRX Discontinuous Reception

eNB evolved NodeB

loT Internet of Things

ISM Industrial Scientific and Medical

LBT Listen Before Talk

LTE Long Term Evolution

LTE-LAA LTE Licensed Assisted Access

LTE-U LTE in Unlicensed spectrum

MSC Modulation and Coding Scheme

MTC Machine Type Communication

NB Narrow Band

PDCCH Physical Downlink Control Channel

PRACH Physical Random Access Channel

PSS Primary Synchronisation Signal

PUCCH Physical Uplink Control Channel

QoS Quality of Service

SIB System Information Block

SRD Short Range Device

SSS Secondary Synchronisation Signal

STA Station

TBTT Target Beacon Transmission Time TSBTT Target Short Beacon Transmission Time

UE User Equipment UL Uplink

WLAN Wireless local area network

References

[1] IEEE P802.11ah™/D5.0, Mar 2015

[2] ETSI EN 300 220

[3] lEEE Std 802.11 , 2012

4] WO 2014/068456 Al, by Renesas Mobile Corporation with the title "Channel Switching Scheme for Wireless Networks"

[5] US 2014/0016568 Al, by Renesas Mobile Corporation with the title "Method and Apparatus for facilitating Channel Switching"

[6] WO 2013/174928 Al, by Ecole Polytechnique Federal De Lausanne (EPFL) with the title "Method of real-time regulation compliance for wireless transmitters"

Claims

1. A node (44; 64) for enabling communication with at least one device (41-43; 61-63) over multiple channels (cl-c3; cl-c6) in a wireless communication network (40; 60), each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum, said node is configured to: obtain a channel switch schedule (70), wherein said channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with said at least one device (41-43; 61- 63), and

- transmit the channel switch schedule (70) to said at least one device (41-43;

61-63).

2. The node according to claim 1, wherein said node (44; 64) is further configured to transmit the channel switch schedule (70) as part of a broadcast transmission (45).

3. The node according to claim 2, wherein said broadcast transmission (45) comprises beacon information or system information.

4. The node according to any of claims 1-3, wherein said channel switch schedule (70) is a periodic schedule.

5. The node according to any of claims 1-4, wherein said node (44; 64) is further configured to: - obtain information of allowed duty cycle for each channel belonging to the unlicensed spectrum, and

obtain allowed transmission time for each channel based on the information of allowed duty cycle for each channel belonging to the unlicensed spectrum, wherein said channel switch schedule is obtained based on the allowed transmission time for each channel.

6. The node according to claim 5, wherein said information of the allowed duty cycle for each channel belonging to the unlicensed spectrum comprises a maximum transmission per a given time period.

7. The node according to claim 6, wherein said node (44; 64) is further configured to: determine a number of allowed transmissions per given time period for each channel belonging to the unlicensed spectrum based on the allowed duty cycle for each channel belonging to the unlicensed spectrum, wherein the allowed transmission time for each channel is further based on the determined number of allowed transmissions per given time period.

8. The node according to any of claims 5-7, wherein said node (44; 64) further is configured to: estimate uplink /downlink traffic for the node (44; 64), wherein said allowed transmission time for each channel is further obtained based on the estimated uplink/downlink traffic.

9. The node according to claim 8, wherein said node (44; 64) is further configured to: determine required transmission time in uplink/downlink per given time period based on the estimated uplink /downlink traffic for the node (44; 64), wherein said allowed transmission time for each channel is further based on the determined required transmission time in uplink/downlink per given time period.

10. The node according to any of claims 1-9, wherein at least one frequency range belongs to a licensed spectrum.

11. The node according to any of claims 1-10, wherein said channel switch schedule (70) comprises at least one anchor channel (71), and wherein said node (44; 64) is further configured to transmit said channel switch schedule (70) to said at least one device (41-43; 61-63) over said at least one anchor channel (71).

12. A method for enabling communication between a node (44; 64) and at least one device (41-43; 61-63) over multiple channels (cl-c3; cl-c6) in a wireless communication network (40; 60), each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum, said method comprises: obtaining (36) a channel switch schedule (70), wherein said channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with said at least one device (41-43; 61-63), and

transmitting (37) the channel switch schedule (70) to said at least one device (41-43; 61-63).

13. The method according to claim 12, wherein said method further comprises transmitting the channel switch schedule (70) as part of a broadcast transmission (45).

14. The method according to claim 13, wherein said method further comprises selecting said broadcast transmission (45) to comprise beacon information or system information.

15. The method according to any of claims 12-14, wherein said channel switch schedule (70) is a periodic schedule.

16. The method according to any of claims 12-15, said method further comprises: obtaining (32a) information of allowed duty cycle for each channel belonging to the unlicensed spectrum, and obtaining (35) allowed transmission time for each channel based on the information of allowed duty cycle for each channel belonging to the unlicensed spectrum, wherein said channel switch schedule (70) is obtained based on the allowed transmission time for each channel.

17. The method according to claim 16, wherein said information of the allowed duty cycle for each channel belonging to the unlicensed spectrum comprises a maximum transmission per a given time period.

18. The method according to claim 17, wherein said method further comprises: determining (32b) a number of allowed transmissions per given time period for each channel belonging to the unlicensed spectrum based on the allowed duty cycle for each channel belonging to the unlicensed spectrum, wherein the step of obtaining (35) allowed transmission time for each channel is further based on the determined number of allowed transmissions per given time period.

19. The method according to any of claims 17-18, said method further comprises: estimating (34a) uplink /downlink traffic for the node, wherein the step of obtaining allowed transmission time for each channel is further based on the estimated uplink/downlink traffic.

20. The method according to claim 19, wherein said method further comprises: determining (34b) required transmission time in uplink/downlink per given time period based on the estimated uplink /downlink traffic for the node, wherein the step of obtaining (35) allowed transmission time for each channel is further based on the determined required transmission time in uplink/downlink per given time period.

21. The method according to any of claims 12-20, wherein at least one frequency range belongs to a licensed spectrum.

22. The method according to any of claims 12-21, wherein said channel switch schedule (70) comprises at least one anchor channel (71), and wherein said step of transmitting (37) the channel switch schedule (70) to said at least one device (41-43; 61-63) further comprises transmitting the channel switch schedule (70) over said at least one anchor channel (71).

23. A device (41-43; 61-63) adapted to communicate with a node (44; 64) over multiple channels (cl-c3; cl-c6) in a wireless communication network (40; 60), each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum, said device is configured to: acquire a channel switch schedule (70) from said node, wherein said channel switch schedule indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the device, and move across multiple channels based on the acquired channel switch schedule.

24. The device according to claim 23, wherein said device is further configured to: estimate uplink and/or downlink traffic for the device, and inform the node of the estimated uplink and/or downlink traffic.

25. The device according to any of claims 23-24, wherein said channel switch schedule (70) comprises at least one anchor channel (71), and wherein said device is further configured to acquire said channel switch schedule (70) from said node over said at least one anchor channel (71).

26. The device according to any of claims 23-24, wherein said channel switch schedule (70) comprises at least one anchor channel (71), and wherein said device is further configured to use said at least one anchor channel (71) as fall-back in case the serving channel cannot be used.

27. A method for enabling communication between a device (41-43; 61-63) and a node (44; 64) over multiple channels (cl-c3; cl-c6) in a wireless communication network (40; 60), each channel occupying a frequency range and at least one frequency range belongs to an unlicensed spectrum, said method comprises: acquiring (81) a channel switch schedule (70) from said node (44; 64), wherein said channel switch schedule (70) indicates a list of serving channels and corresponding serving time durations for use by the node to communicate with the device and moving (82) across multiple channels based on the acquired channel switch schedule (70).

28. The method according to claim 27, wherein said method further comprises: estimating (84) uplink and/or downlink traffic for the device, and informing (85) the node of the estimated uplink and/or downlink traffic.

29. The method according to any of claims 27-28, wherein said channel switch schedule (70) comprises at least one anchor channel (71), and wherein said step of acquiring (81) said channel switch schedule (70) from said node comprises acquiring the channel switch schedule (70) over said at least one anchor channel (71).

30. The method according to any of claims 27-28, wherein said channel switch schedule (70) comprises at least one anchor channel (71), and wherein said method further comprises using said at least one anchor channel (71) as fall-back in case the serving channel cannot be used.