Method and apparatus for network management using periodic measurements of indicators

Method and device for measuring and managing network using indicator period

The present invention relates to beacon measurement request signals and network management used in wireless slotted communications. In particular, the present invention relates to network management using periodic parameter measurement, such as new beacon received power level or signal quality.

IEEE 802.11 communication allows users to roam between multiple access points that may operate on the same or separate channels. IEEE 802.11 communication usually takes effect through wireless LAN access points (APs), which are usually a single independent unit, but may include networks with multiple APs that provide roaming functions. To support the roaming function, each access point usually transmits a beacon signal every 100 ms. A roaming station (STA) uses this beacon to measure the strength of its existing access point connection. If the STA senses a weak signal, the roaming STA can implement a re-association service to connect to the access point that transmits a stronger signal.

IEEE 802.11 supports two power modes; drive and power saving (PS). The agreement between the basic network and the hoc network is different. In the basic network, there is a mode for AP to monitor each mobile station. The station in drive mode is fully powered and can therefore transmit and receive at any time. Conversely, stations in PS mode are only periodically woken up to check for incoming packets that may come from the AP. A station always informs its AP when it changes mode. The AP periodically transmits beacon frames separated by a fixed beacon interval. Any AP should monitor these boxes. A traffic indication map (TIM) is transmitted in each beacon box. The beacon box contains the IDs of the PS stations that have buffered unicast packets in the AP. The AP should stay awake for the remaining beacon interval when it receives its ID. Under the connection period (ie, DCF), the awakened PS station can send a PS-POLL to the AP in order to retrieve the buffered packet. In the contention-free period (ie, PCF), the PS station waits for the AP to poll it. The AP transmits TIMs (DTIMs) in the beacon box to indicate buffered broadcast packets. The delivery TIMs are separated by a fixed number of beacon intervals. Just after the DTIMs, the buffered broadcast packets are transmitted.

Because IEEE 802.11 assumes that mobile stations are fully connected, the transmission of a beacon frame can be used to synchronize the beacon intervals of all stations. In addition to the use in IEEE 802.11, the beacon signal is generally useful in other WLAN communications and wireless communications. Periodic measurements are implemented in systems implementing the 3rd Generation Partnership Project (3GPP) Wide Frequency Division Code Multiple Access System (W-CDMA). This type of system uses a time-sharing duplex mode. In order to support the higher-level functions of the IEEE 802.11 standard for efficient network management, it is desirable to have several physical parameters for different forms of network management.

One of these parameters is the pre-received signal-to-noise indicator (PSNI). Its measurement provides a quantitative and comparative measure of the quality of the received signal used in all channels/rates and all physical channels and between all stations. Measurement. Another parameter is the received channel power indicator (RCPI) index measured at the antenna connector, which is a measurement of the received RF power in the selected channel. The RCPI parameter can be a measurement of the PHY sublayer of the received RF power in the channel being measured on the PLCP header (preamble) and the entire received frame. RCPI is a logarithmic function defined in dBm that is monotonically increased by the received power level. The exemplified allowable value of the RCPI parameter can be an 8-bit value in the range from 0 to 220.

In the known method, the parameters RCPI and PSNI are measured as a single measurement. This method has some defects. It is hoped to provide improved methods for parameter measurement, such as RCPI and PSNI, to produce specific advantages in more efficient network measurement.

According to the present invention, the periodic measurement required by the new beacon is used to support roaming and dynamic data rate adjustment and related functions. The concept of periodic measurement is implemented in a manner analogous to the periodic measurement in the implementation of the third-generation partnership project (3GPP) wideband code division multiple access (W-CDMA) system using the time-division duplex mode.

Hereinafter, a wireless transmission/reception unit (WTRU) includes but is not limited to user equipment, mobile stations, fixed or mobile subscriber units, pagers, or any other types of devices capable of operating in a wireless network environment. When referring to the following, access points include but are not limited to point B, location controllers, access points, or any other type of interface device in the wireless environment.

The "Access Point (AP)" in a typical IEEE 802.11 implementation is a station or device that provides wireless access for a device to establish a wireless connection with a LAN, and to establish a part of a wireless LAN (WLAN). If the AP is a fixed device on the WLAN, the AP is a station that transmits and receives data. This AP allows the WTRU to connect to a network, assuming that the WLAN itself has a connection to the network.

By performing parameter measurements, such as RCPI and PSNI, network management is performed periodically instead of one measurement. The impact of performing periodic measurements on network performance and the accompanying benefits are described in the preferred embodiment. In particular, it describes the beneficial effects of performing periodic measurements on beacon request extensions to support roaming and dynamic data rates. Even if the present invention is described in the content of a specific standard IEEE 802.11, the present invention is expected to be applicable to other solutions.

Periodic beacons are required to be performed during a connection between a WTRU and an AP on a WLAN. The measurement request area corresponding to the beacon request includes a measurement period value and the channel number to which the request applies. This beacon requires a scan mode, which includes an "active scan" mode, a "passive scan" mode, and a "beacon table" mode. In the active scanning mode, the measuring station (STA) transmits one of the detection requirements with the broadcast service station identification (SSID). The STA beacon report in this measurement includes the information element of each STA from which it detects a beacon or probe response, regardless of whether the probe response is triggered by the probe request of the STA under measurement. In the passive scanning mode, the STA under measurement passively receives and responds to an information element containing an information element for each STA on a specific channel, from which it detects a beacon or probe response. If the channel under measurement is also the channel in service, the STA will perform its normal data flow operation at the same time. In the beacon table mode, the measuring STA returns the current content containing its beacon table without performing additional measurements. The measurement period area is set to be equal to the required measurement period, expressed in time units (TUs).

The following are some potential advantages of periodic measurement compared with single good method:

Periodic measurement reduces management traffic: a single measurement requires multiple reports, but only when relevant.

The absolute threshold telecommunications (crossings) on the PSNI measurement are ideal for triggering data rate changes.

The absolute threshold on the RCPI measurement is ideal for proximity detectors for telecommunication locations.

Relative to the relative threshold of the AP in service to detect and transmit the situation.

This beacon request also includes the period extension (information area) of the specified period beacon measurement. This extended area is used to provide periodic measurement parameters and measurement results report. These provide periodic measurements that reduce management traffic, so a single measurement requires multiple reports to be generated. These multiple reports are only provided when they are deemed relevant. The absolute threshold telecommunications on the pre-received signal-to-noise indication (PSIN) can be used as a condition for providing a measurement report. These measurements on PSNI are suitable for triggering data rate changes. The absolute critical telecommunication on the received channel power indicator (RCPI) can be regarded as providing a measurement report.

This periodic extension is used as an additional area in the beacon requirement for periodic beacon measurement. The capacity for performing periodic measurement is the selective capacity used by APs, and therefore APs that cannot perform periodic beacon measurement will ignore these periodic extensions. The beacon report is a requirement to perform a measurement. The beacon report contains the response to the requested beacon measurement.

These absolute threshold telecommunications are suitable for proximity detectors used to determine the position relative to an AP and the proximity position. A relative threshold relative to an AP in a service is used to detect handoff conditions.

The measurement request area corresponding to the beacon is shown in Table 1, and includes the measurement period and channel number used for this request. Table 1 also includes extensions (additional information areas) required for specifying periodic measurements and condition reports. Table 1 roughly shows the format of the measurement request area required by a beacon. The description of the current measurement indicates the 8-bit (octets) number used in the channel number, frequency band, measurement period, and scan mode. For comparison, Table 1 also shows the 8 bits relative to the basic service setting identification (BSSID), measurement period, report status, criticality/offset, and periodic extension of the hysteresis effect. In particular, the measurement request area corresponding to a beacon request is shown in Figure 1 and includes the measurement request and channel number used by the request. The response to the beacon request is a beacon report.

<tables><img file="TW200529602A_D0001.tif" /></tables>

If the AP cannot perform periodic measurements and therefore cannot recognize these extensions, the AP ignores the extensions and provides a single measurement and a single report.

In Table 1, the channel number indicates the channel number where the requested STA commands the received STA to report the detected beacon and the search response. In the beacon request, the channel number area indicates the requesting STA instructs the receiving STA to report the detected beacon and the channel number where the search response is located. The frequency band area indicates, from Table 1, the frequency band in which the receiving STA performs its measurement. The scan mode area is set to scan type, according to Table 2 (below). These scanning behaviors are as follows:

-In the active scanning mode, the measured STA transmission has the exploration requirement of the broadcast SSID. The beacon report of the measuring STA includes the information element of each STA. The STA detects a beacon or probe response from the report, regardless of whether the probe response is triggered by the probe request of the measuring STA itself.

-In the passive scanning mode, the measuring STA passively receives and sends back a beacon report containing an information element for each STA on a specific channel, and the STA detects a beacon or probe response from the report. If the measurement channel is also a service channel, the STA performs its normal data flow operation at the same time.

-In the beacon table mode, the measuring STA sends back a beacon report containing the current contents of its beacon table without performing additional measurements.

The measurement period area is set to be equal to the required measurement period, expressed in TUs.

Tables 2 and 3 show the definition of the frequency band required for wireless measurement and the definition of the scanning mode used by the beacon requirement element.

<tables><img file="TW200529602A_D0002.tif" /></tables>

<tables><img file="TW200529602A_D0003.tif" /></tables>

The BSSID indicates the specific AP for which this measurement is required. This BSSID designates which AP to measure when several APs are detectable on a predetermined channel. This BSSID is set as the broadcast BSSID, when this measurement is performed on any AP(s) on this channel. The broadcast BSSID is used when an AP BSSID is unknown.

The measurement period indicates whether the measurement is a single measurement event or a periodic measurement that is repeated in each measurement period. This measurement period is divided into secondary areas: unit and period. The unit sub-region defines the time unit used in the periodic sub-region and consists of 2 MSBs with the following values.

This cycle sub-region is composed of 14LSBs and represents an unsigned integer of the repetition time interval of the cycle measurement. A value of 0 in the periodic subarea means that the measurement is not periodic but a single measurement. The period sub-area value of 16383 (3FFF Hex) means that the measurement is periodic with an unrequired period measurement period; in this case, the measurement is performed on the basis of the best results and performed as frequently as the situation allows.

The report situation defines when the measured result is reported to the requesting STA. The value of this report is defined in Table 4.

<tables><img file="TW200529602A_D0004.tif" /></tables><tables><img file="TW200529602A_D0005.tif" /></tables>

Threshold/offset provides the threshold or offset that will be used by the situation report. A threshold is an unsigned 8-bit integer equal to PSNI or RCPI units. The offset value is a signed 7-bit integer in the range of (-127, +127).

The hysteresis supply unit is equal to the unsigned 8-bit integer hysteresis value of the unit used in the critical value/offset area.

Figure 1 is a diagram of a network structure 11, in which one or more WLANs 12, 13 communicate with a WTRU 15 via one or more APs 17-19. In this embodiment, it is described that the WLANs 12, 13 can establish a network connection 22, either directly or via a radio network controller (RNC) 23.

Figure 2 shows the measurement or report type, which shows how an event triggers a report, or triggers a periodic report. In particular, Figure 2 is for comparison, showing a single report of PSNI and RCPI when compared with the absolute threshold, the threshold of the AP in service, and the periodic range of the service AP using similar periodic reports. It also indicates the periodic report for each trigger event for comparison. The widest scope is to measure 26. The "measurement" used here can be a measurement or a report. The measurement 26 can be a single 27 or periodic 28 measurement. A single measurement generates a single report 29, which includes a single report PSNI 30 and a single report RCPI 31. This periodic measurement 28 can generate a situation report 32 or a periodic report 33. This situation report 32 can provide an absolute threshold 34, an in-service AP threshold 35, or an in-service AP cycle range 36. The absolute neighbor value 34 includes an absolute critical value PSNI 37 and an absolute critical RCPI 38. The in-service AP threshold 35 includes an in-service AP threshold PSNI 47 and an in-service AP threshold RCPI 48. The in-service AP period range 36 includes an in-service AP period range PSNI 57 and an in-service period range RCPI 58. The periodic report 33 includes a periodic report PSNI 67 and a periodic report RCPI 68.

In addition, this single report 31 can be conditionally reported based on an absolute critical value 34 including an absolute critical value PSNI 37 and an absolute critical value RCPI 38. At the same time, the single report 31 can be conditionally reported based on the in-service AP threshold 35 including one of the in-service AP threshold PSNI 47 and the in-service AP threshold RCPI 48. The AP periodic range in this service is a single report 31 and is not used, but periodic measurement reports can be provided to include the AP periodic range PSNI 57 in the service and the AP periodic range 36 in the service periodic RCPI 58.

The single and periodic measurements 27 and 28 are measurement types. The single report 31 and the situation report 32 periodically report the absolute threshold 34, the in-service AP threshold 35, and the in-service AP periodic range 36 trigger events. The measurement results are single report PSNI 27, single report RCPI 28, absolute critical value PSNI 37, absolute critical value RCPI 38, serving AP critical value PSNI 47, serving AP neighboring value RCPI 48, serving AP periodic range PSNI 57. AP Periodic Range RCPI 58 in Service, PSNI 67 Periodic Report and RCPI 68 Periodic Report. For situation reports, event detection triggers one or more of these single event report output or periodic report output.

Figure 3 is a graph showing the influence of the absolute critical value on the data rate selection, and shows the changes in the measurement quality of the three different channels of 5.5 Mbps, 2.0 Mbps, and 1.0 Mbps over time. At the start time of the chart, when measuring at the STA, STA1 receives a low PSNI level from one of the APs, which is substantially lower than an absolute critical value. This rate is established at 1 Mbps. STA2 and STA3 have PSNI levels higher than the critical level. When the time elapses, the STA 3 has received a PSNI level that exceeds a second threshold, and then drops below the absolute threshold. STA 3 can therefore change to a rate of 5.5 Mbps, but must drop to a rate of 2 Mbps and eventually 1 Mbps, as the PSNI level drops. STA2 remains at 2 Mbps until later when STA 2 has enough PSNI level to change to 5.5 Mbps. These changes in the PSNI level can also be used to change APs, by choosing a higher rate or PSNI level, if the resources from the AP are available.

Figure 4 is a graph showing the relative threshold of one of the APs in a delivery service. This graph also shows the change in the measured product value of AP1 and AP2 at one of the performance report events over time. This chart shows signals from a STA of a first AP (AP in service) and a second AP (AP2). The measurement of the AP in service is reduced by an offset value, where the PSNI is lower in order to benefit AP2. Therefore, the PSNI measurement of the AP in service is skillfully reduced by this offset. This causes early triggering of the transfer due to this offset.

Figure 5 is a graph showing the effect of report drift, and shows the relative critical triggers of AP1, 2 and 3 in the report range and when the report is terminated. This chart shows the ISCP threshold and reported events of the time slot ISCP corresponding to the time. The triggered event and the periodic report of the PSNI level each represent an example of the reduced PSNI level due to the offset. The report of AP 3 in service continues during one of the peak periods of the PSNI reported from a third AP, AP3, but does not continue when the signal from AP3 drops below the PSNI offset report from the AP in the service.

Figure 6 is a graph showing the RCPI level of AP in service. The trigger event here is an absolute critical value exceeded. This trigger event triggers a report.

Although the features and elements of the present invention are described in specific embodiments, each feature can be used alone (other features and elements of the preferred embodiment are not required), or used in combination with or without other features and elements of the present invention .

<p>22Internet connection</p><p>23Wireless Network Controller</p><p>26Measurement</p><p>27Single</p><p>28Periodic</p><p>29Single report</p><p>32 Situation report</p><p>33Periodic report</p><p>34Absolute critical value</p><p>35AP threshold in service</p><p>36AP period range in service</p>

Figure 1 is a diagram of a network structure in which WLANs communicate with a wireless transmission/reception unit (WTRU) via one or more access points.

Figure 2 is a graph showing the type of measurement or report.

Figure 3 is a graph showing the influence of the absolute critical value on the data rate selection.

Figure 4 is a graph of the relative thresholds of APs in a service using a handoff.

Figure 5 is a chart reporting the effects of drift.

Figure 6 is a graph showing the received channel power indicator (RCPI) of the AP in service.