Source: https://patents.google.com/patent/US9203532B2/en
Timestamp: 2020-01-27 04:08:35
Document Index: 93151079

Matched Legal Cases: ['§371', 'Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 61', 'Application No. 12005571', 'Application No. 201180004740', 'Application No. 11737281']

US9203532B2 - Station operation method and apparatus in TV whitespace - Google Patents
US9203532B2
US9203532B2 US13/570,000 US201213570000A US9203532B2 US 9203532 B2 US9203532 B2 US 9203532B2 US 201213570000 A US201213570000 A US 201213570000A US 9203532 B2 US9203532 B2 US 9203532B2
US13/570,000
US20120314658A1 (en
2011-01-26 Priority to PCT/KR2011/000545 priority patent/WO2011093642A2/en
2012-03-12 Priority to US201213395564A priority
2012-04-30 Priority to US13/459,826 priority patent/US8605741B2/en
2012-08-08 Priority to US13/570,000 priority patent/US9203532B2/en
2012-08-08 Application filed by LG Electronics Inc filed Critical LG Electronics Inc
2012-12-13 Publication of US20120314658A1 publication Critical patent/US20120314658A1/en
2015-12-01 Publication of US9203532B2 publication Critical patent/US9203532B2/en
101700062884 EMD family Proteins 0 description 114
101700077399 ST2A2 family Proteins 0 description 114
101700061797 STA family Proteins 0 description 114
108700000006 regulatory domains Proteins 0 description 3
The present invention relates to a channel switching scheme. By this scheme, a first station transmits a channel switching request frame comprising target channel information and transmit power control information for the target channel to a second station. And, the second station transmits a channel switch response frame to the first station. After these, the second station transmits a signal on the target channel. Here, parameters in the above transmit power control information are used for transmit power control calculation of the second station for the target channel.
This application is a continuation of U.S. patent application Ser. No. 13/459,826, filed on Apr. 30, 2012 now U.S. Pat. No. 8,605,741; which is a continuation of U.S. patent application Ser. No. 13/395,564, filed on Mar. 12, 2012; which is a National Stage of and claims the benefit under 35 U.S.C. §371 of International Application No. PCT/KR2011/000545, filed on Jan. 26, 2011; which claims the benefit of U.S. Provisional Application No. 61/298,213, filed on Jan. 26, 2010, U.S. Provisional Application No. 61/417,288, filed Nov. 26, 2010, U.S. Provisional Application No. 61/417,269, filed Nov. 25, 2010, and U.S. Provisional Application No. 61/420,769, filed on Dec. 7, 2010; the entire disclosure of each of which is incorporated herein by reference for all purposes.
The present invention relates to a station (hereinafter, referred to as ‘STA’) operation method and apparatus in TV whitespace.
TV whitespace (referred to as ‘TVWS’ hereinafter) is a frequency allocated to broadcast TV and can include UHF and VHF bands. While the TVWS can include 54 MHz to 698 MHz (US and Korea), part of these frequency bands may not be used for unlicensed devices in some countries.
Unlicensed devices using TVWS need to provide a protection function for operations of licensed devices (which may be referred to as ‘incumbent users’ or ‘primary users’). That is, when an incumbent user such as a microphone uses a specific band used by an STA, the STA needs to stop using a channel corresponding to the band in order to protect the incumbent user.
The available channel information request message may include a category field that indicates the category of the available channel information request message, an action value field that indicates an action to be performed through the available channel information request message in the category, a source address field that indicates: the address of a device transmitting the available channel information request message, a destination address field that indicates a device receiving the available channel information request message, and a field that indicates identification information on a plurality of available channels.
A database 1210, for example, a TV band database may have information on available channels in a TV band. This database information includes considerably accurate location-based information of about 50 m, in general. An RLS (Registered Location Server) 1220 may be a server including information on registered locations of all APs operating in TVWS. While FIG. 1 illustrates the TV band database 1210 and the RLS 1220 as separate devices, they may be implemented as one TV band database device.
If an STA operating as an unlicensed device in TVWS needs to operate as an AP, the STA should register the location thereof in the RLS 1220. The AP 1230 can acquire available channel information of the database according to registrations. Then, the AP 1230 can provide the database information to the STAs 1240 chat belong thereto.
TABLE 1 Order Information 1 Category 2 Action 3 Destination MAC Address 4 Source MAC Address 5 Supported Channels
Different maximum power levels may be allowed for available channels that can be used by unlicensed devices in TVWS. For example, when CH1, CH2 and CH3 are indicated as available channels, different maximum transmit power levels may be allowed for the respective channels in consideration of the influence on a neighboring channel. For example, maximum transmit power values of 40 mW, 100 mW and 40 mW can be respectively allowed for CH1, CH2 and CH3. Information on a maximum allowable power level in an available channel can indicate the maximum allowable power for the available channel. This maximum allowable power may be maximum allowable power conforming to FCC regulations.
TABLE 2 Order Information 1 Category 2 Action 3 Destination MAC Address 4 Source MAC Address 5 Target Channel(s) 6 White Space Available Time(s) 7 Power Constraint(s)
Category, action value, destination address, and source address fields in Table 2 correspond to those shown in Table 1. In Table 2, “Target Channel(s)” may include (a) identification information on an available channel that will be used by an STA receiving the available channel information response message for a WLAN operation, and “White Space Available Time(s)” may include (b) information on valid time of the available channel. Further, “Power Constraint(s)” may represent maximum allowable transmit power for each available channel.
As described above, information on the device type to which the WSM is applied is added to the WSM in the current embodiment because device types may have different available channels and maximum allowable power values. Fixed devices cannot use a channel next to a TV channel being used by an incumbent user. However, personal/portable devices can use the channel next to the TV channel being used by the incumbent user on the condition that the maximum allowable power value of the channel is reduced from 100 mW to 40 mW.
Therefore, the WSM preferably includes device type information along with available TV channel numbers and maximum transmit power field corresponding to each available TV channel. FIG. 3 shows that a fixed device operating as a master transmits a channel map (e.g. WSM) to another fixed device and a personal/portable device operating as clients. Specifically, the fixed device operating as a master respectively adds a device type corresponding to the other fixed device operating as a client and a device type corresponding to the personal/portable device to a WSM, transmits the WSM for the other fixed device (WSM having a device type field indicating the fixed device) to the other fixed device, and sends the WSM for the personal/portable device (WSM having a device type field indicating the personal/portable device) to the personal/portable device.
In FIG. 4, on the assumption that the first channel is TV channel #21 and the last channel is TV channel #25, when TV channels #21 and #25 are occupied by an incumbent user, a fixed device can operate at a maximum power of 100 mW in TV channel #23 other than neighboring channels #22 and #24 of the TV channels #21 and #25 occupied by the incumbent user. A personal/portable device can operate at a maximum power of 40 mW in the neighboring channels #22 and #24 and at a maximum power or 100 mW in TV channel #23.
The WSM can include the field indicating valid time information on each available channel. The valid time field may indicate valid time information on each available channel or valid time information for the overall WSM. If the WSM is for a fixed device, the valid time field can include valid time information on each available channel. However, a device such as an STA belonging to a specific AP (referred to as ‘first mode device’ hereinafter) may not require the valid time information on each available channel. The first mode device may check whether the received WSM is valid by receiving an acknowledgement signal at predetermined intervals (e.g. every 60 seconds). Valid time information may be determined or omitted according to device type.
The channel scheduling request frame can include channel scheduling information, that is, a channel list used to obtain available start time and an available duration of a specific TV channel. In FIG. 6, “Available Channel Number” field can indicate the channel list. For example, if available channels are CH1, CH2, CH3, and CH4, the channel scheduling request frame including channel numbers 1, 2, 3 and 4 can be transmitted. In this example, it is assumed that the enabling STA or dependent AP that requests channel scheduling information previously knows the available channels through the WSM.
In FIG. 6, “RequesterSTAAddress” indicates the address of the device that transmits the channel scheduling request frame. “ResponderSTAAddress” represents the address of a device that receives the channel scheduling request frame. “Length” can have a value depending on the number of available channels related with the channel scheduling information. “Available Channel Number” can indicate an available channel number corresponding to the channel scheduling information.
In FIG. 7, “RequesterSTAAddress” indicates the address of a device that transmits a channel scheduling request frame. “ResponderSTAAddress” represents the address of a device that receives the channel scheduling request frame. “Length” indicates the overall length of channel scheduling information. “Available Channel Number” indicates an available channel corresponding to the channel scheduling information. “Available Start Time” can represent start time of an available duration of an available channel and “Available Duration” can indicate the available duration of the available channel.
If an STA cannot secure database information based on regional location information thereof, the STA corresponds to a sensing only device and transmit power in a target channel is limited to 50 mW. On the contrary, if the STA can secure the database information, the STA can use up to 100 mW as transmit power even in the target channel.
TABLE 3 Order Information 1 Category 2 Action 3 Channel Switch Announcement element 4 Secondary Channel Offset element 5 Backup Channel element
TABLE 4 Element ID Length Backup Channel Number Octets: 1 1 1
In the WSM format shown in FIG. 8, a “country code” field provides information on the location of a channel map following this field. That is, countries may have different TV bands and TV channel bandwidths, and different regulatory domains are assigned to the countries. Accordingly, the country code field helps recognize the physical location of a TV channel available for an STA that receives the WSM along with a channel map field. The country code field can signal a country string value of 3 octets. That is, the first 2 octets indicate a country code defined in ISO/IEC 3166-1 and the last octet means an environment. The country code field can include more detailed information than country information in an extensive manner. For example, the country code field can include a regional code value of a specific country.
Although the basic unit of a channel map that signals whether or not a channel is available is not limited to a TV channel bandwidth, it can be channel information in the smallest basic unit provided by a database of a corresponding regulatory domain. When the smallest basic unit constituting an available channel list provided by a database of a TVWS band is a TV channel bandwidth, the basic unit of a channel map becomes a TV channel bandwidth. The TV channel bandwidth of America and Korea is 6 MHz and some countries have TV channel bandwidths of 7 MHz and 8 MHz.
In FIG. 9, a WSM includes device type information, available channel numbers (N, M, . . . , K), maximum allowable power in each available channel, and information on valid time applied to the entire WSM. As described above, it is more desirable to inform a first mode device of the valid time for the entire WSM received by the first mode device rather than information on valid time for each available channel. In this case, the WSM format shown in FIG. 9 can be used.
FIG. 10 shows a WSM including device type information, available channel numbers (N, . . . , K), maximum allowable power in each available channel, and information on valid time for each available channel. As described above, it is desirable to inform a fixed device or a second mode device of information on valid time for each available channel. In this case, the WSM format shown in FIG. 10 can be used.
TV channels available for transmission between TVWS 802.11 AP and STA have a bandwidth of 6 MHz in the US and correspond to channel numbers 21 to 51. That is, it is necessary to indicate whether primary users are present in 30 TV channels. A bitmap for. TV channels #21 to #51 can be configured in ascending order or descending order in such a manner that a channel in which a primary user is present is indicated by 0 (unavailable) and a channel in which a primary user is not present is indicated by 1 (available) or vice versa.
The device type indicates whether the corresponding channel map corresponds to a TV channel assigned to a personal/portable device or to a TV channel assigned to a fixed device. If the device type is 0, a channel bitmap (bits 1 to 30) may be bitmap information on TV channels #21 to #51. It may be necessary to indicate whether primary users are present in 54 to 60 MHz, 76 to 88 MHz, 174 to 216 MHz and 470 to 512 MHz which are assigned for communication between fixed devices when an STA that receives the channel map is a fixed device or as occasion demands. For this, when the device type is 1, bits 1 to 18 may be recognized as bitmap information.
In FIG. 11, “starting channel number (S)” represents the number of a TV channel from which a bitmap is started. “Number of channels (L)” represents the number of channels starting from the starting channel number in the bitmap indicated in the channel map. The length of the channel bitmap following “number of channels” field depends on the value of the “number of channels” field.
FIGS. The channel maps shown in FIGS. 14 and 15 are used to signal a center frequency and an available band using a channel bandwidth when a frequency band that can be used at a specific time in a specific location is signaled. For example, if a frequency of 10 MHz on each of both sides of 690 MHz is available, this frequency band is signaled using a center frequency of 690 MHz and a channel bandwidth of 20 MHz. Here, maximum allowable transmit power for the frequency band can be signaled along with the frequency band. An available frequency band for each available channel block is signaled in this manner.
In an exemplary embodiment of the present invention, valid time information is signaled for each tuple. Since channels use frequencies in different patterns, the channels have different available durations. Accordingly, it is desirable to signal valid time information for each channel. However, when valid time information on a plurality of frequency blocks is signaled, signaling valid time for each available channel may increase overhead. Therefore, it may be more advantageous to signal a list of channels available the moment and valid time information on a currently signaled channel map according to the system, and thus in an embodiment of the present invention, a channel map includes valid time information on the entire channel map. In this case, the shortest valid time from among valid times of available channels signaled by the channel map is signaled.
Whether or not a specific channel is available depends on time. A value indicating how long channel availability information included in a channel map is valid for a device that currently transmits WM corresponding to the channel map is valid time information. When time information of the valid time field indicates that the channel availability information is valid until a specific time, the time information can be indicated as absolute time or relative time.
For example, a WSM or channel map indicating that channel #3 is available at a maximum transmit power of 100 mW can be transmitted to the fixed device, and a WSM or channel map indicating that channel #3 is available at a maximum transmit power of 100 mW and channels #2 and #4 are available at a maximum transmit powers of 40 mW can be transmitted to the personal/portable device in the situation of FIG. 4.
In this embodiment, a WSM or channel map indicating that channel #3 is available at a maximum transmit power of 100 mW, as shown in FIG. 18, can be commonly transmitted to the fixed device and the personal/portable device, and then a WSM or channel map having a device type set to the personal/portable device and indicating that channels #2 and #4 are available at a maximum transmit power of 40 mW, as shown in FIG. 19, can be additionally signaled in the situation of FIG. 4. Here, it is desirable to transmit the additionally signaled WSM using the same MAP ID as that of the commonly signaled WSM such that devices receiving the WSMs can easily combine the WSMs having the same MAP ID.
TABLE 5 Device Type Description 0 Reserved 1 Fixed and Personal/Portable Device 2 Fixed Device 3 Personal/Portable Device 4 Personal/Portable Device (Spectrum Mask Class A) 5 Personal/Portable Device (Spectrum Mask Class B) 6-255 Reserved
In a band in which a channel available for unlicensed devices is varied by a licensed device temporally and spatially, such as TVWS, operation of an unlicensed device may interfere with the licensed device when a spectrum mask used by an AP in specific BSS is different from a spectrum mask used by STAB. That is, when the AP accesses a database to acquire an available channel list, the database signals a specific channel as an available channel on the condition that the licensed device does not use the channel at corresponding time on the assumption that the unlicensed device meets out-band-emission requirement for neighboring channels. According to current FCC regulations, the spectrum mask with respect to out-band emission for neighboring channels is −55 dBr. When a DTV uses channels #13 and #15 and does not use channel #14, for example, the database can signal channel #14 as an available channel. However, it is necessary to meet out-band-emission requirements of channels #13 and #15 in order to use channel #14. Accordingly, if the spectrum mask of a specific STA belonging to the AP is less strict than the spectrum mask of the AP and thus it does not satisfy regulations, the corresponding system is regarded to violate the regulations even though the spectrum mask of the AP perfectly meets the out-band-emission requirement. Therefore, exchange of information on spectrum masks needs to be performed in an association procedure after the AP receives the available channel list according to the above condition.
The STA preferably includes information on the spectrum mask thereof in a probe request frame, and (re-) association request and transmits the information. If the spectrum mask of the STA is not stricter than the spectrum mask used by the AP, the AP can designate a transmit power level that can be used by the STA for each spectrum mask.
1. A method for channel switch in a wireless communication system, the method comprising:
receiving, at a second station, an available channel information message from a device having database information, the available channel information message comprising:
identification information for an available channel;
information on a device type to which the available channel information message can be applied; and
when the information on the device type corresponds to a fixed device or a second mode device having an authority to directly access the database information, the available channel information message includes information on a valid time of the available channel,
wherein the second station operates on the available channel based on the received available channel information message;
receiving, at the second station from a first station, a channel switch request frame comprising target channel information and transmit power control information for the target channel;
transmitting, by the second station to the first station, a channel switch response frame; and
transmitting, by the second station to the first station, a signal on the target channel,
wherein parameters in the transmit power control information of the channel switch request frame are used for calculation of transmit power of the signal transmitted by the second station on the target channel, and
wherein the information on the valid time is not included in the available channel information message when the information on the device type corresponds to a first mode device having no authority to directly access the database information.
2. The method according to claim 1, wherein the transmit power control information comprises maximum transmit power information for the target channel.
3. The method according to claim 1, wherein the transmitting the signal on the target channel is performed over a direct link between the first station and the second station.
4. The method according to claim 1, wherein the channel switch comprises a Tunneled Direct Link Setup (TDLS) channel switch.
5. The method according to claim 1, wherein the target channel comprises an off-channel that is not used by an Access Point (AP).
6. The method according to claim 1, wherein a maximum transmit power on the target channel is determined, by the second station, as a lowest transmit power value among different transmit power values included in the transmit power control information.
7. A station supporting channel switch in a wireless communication system, the station comprising:
receive, at the station operating as a second station, an available channel information message from a device having database information, the available channel information message comprising:
when the information on the device type corresponds to a fixed device or a second mode device having an authority to directly access the database information, the available channel information message includes information on a valid time of the available channel;
receive, at the station, operating as the second station, from a first station, a channel switch request frame comprising target channel information and transmit power control information for the target channel; and transmit, from the station, operating as the second station, to the first station, a channel switch response frame; and a processor configured to:
operate on the available channel; and
control the transceiver to perform transmitting a signal on the target channel,
wherein parameters in the transmit power control information of the channel switch request frame are used for calculation of transmit power of the signal transmitted from the station, operating as the second station, on the target channel, and
8. The station according to claim 7, wherein the transmit power control information comprises maximum transmit power information for the target channel.
9. The station according to claim 7, wherein the processor controls the transceiver to transmit the signal on the target channel over a direct link between the first station and the second station.
10. The station according to claim 7, wherein the channel switch comprises a Tunneled Direct Link Setup (TDLS) channel switch.
11. The station according to claim 7, wherein the target channel comprises an off-channel that is not used by an Access Point (AP).
12. The station according to claim 7, wherein a maximum transmit power on the target channel is determined, by the second station, operating as the second station, as a lowest transmit power value among different transmit power values included in the transmit power control information.
US13/570,000 2010-01-26 2012-08-08 Station operation method and apparatus in TV whitespace Active 2031-03-23 US9203532B2 (en)
PCT/KR2011/000545 WO2011093642A2 (en) 2010-01-26 2011-01-26 Station operation method and apparatus in tv whitespace
US201213395564A true 2012-03-12 2012-03-12
US13/459,826 US8605741B2 (en) 2010-01-26 2012-04-30 Station operation method and apparatus in TV whitespace
US13/570,000 US9203532B2 (en) 2010-01-26 2012-08-08 Station operation method and apparatus in TV whitespace
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