CN1857016B - Wireless communication method and apparatus for performing access point start and primary channel selection - Google Patents

Abstract

A startup process of an access point (AP) includes a discovery phase and an announcement phase. During the discovery phase, the AP detects neighboring APs from its own extended service set (ESS), neighboring APs from different ESSs, and external sources of interference. During the announcement phase, the AP transmits its beacon signals at maximum power in order to accelerate recognition by neighboring AP running the discovery phase. An automatic initialization channel selection process of an AP scans channels the AP will use to communicate. Information of each scanned channel is recorded and a best performance channel is determined for use by the AP.

Description

Wireless communication method and device for implementing access point activation and preliminary channel selection process

technical field

The present invention relates to a wireless communication system. More particularly, the present invention relates to initializing operating parameters and selecting the most appropriate operating channel for an access point (AP).

Background technique

The conditions of a radio link over which a wireless communication system operates may change at any time. As a wireless transmit/receive unit (WTRU) is mobile, the WTRU may be out of range or within range of one or more APs depending on its location. When an AP is just established or restarted after being shut down for some reason, the startup process of the AP must evaluate its radio resource environment. In general, the activation process also provides a mechanism for announcing its own presence to other APs of its own Extended Service Set (ESS), so that other APs can self-adjust their own operating parameters accordingly.

Several architectures are used today to increase the capacity of wireless communication systems. Channel (ie, frequency) selection is one such architecture whereby one or more APs within a network select one or more channels to communicate with other associated WTRUs. Coordination of AP channel selection is generally performed manually. However, it is very impractical to manually coordinate channel selection in response to every small change in the network configuration, since it may result in a redesign and reconfiguration of all APs. Unlicensed spectrum and external sources of interference can also create problems that manual coordination cannot adequately resolve. In addition, it is difficult to assign channels by manual channel selection in such a way that the traffic load of adjacent APs is shared among the available channels in a manner that maximizes the overall system capacity.

Conventional architectures encounter another problem when multiple APs try to power on at the same time. When this happens within a network, all APs try to make a channel selection at the same time. Therefore, the channel selection of the APs will not be optimal because each AP does not take into account the channel selections of neighboring APs.

A method and system that overcomes the aforementioned problems would be highly advantageous.

Contents of the invention

The present invention proposes a method and device for implementing an AP start-up and preliminary channel selection process.

The start-up process of the AP includes a path loss discovery step and a notification step. During the path loss discovery step, the AP detects neighboring APs from its own ESS, neighboring APs from different ESSs, and external sources of interference. During the advertising step, the AP transmits a beacon signal in order to speed up recognition by neighboring APs that are running the path loss discovery step. The start-up process provides the AP with the ability to monitor and assess its radio environment, thus allowing the AP to self-determine initial operating parameters.

An AP initialization channel selection process is performed automatically at the beginning of the AP's start-up process.

Description of drawings

The invention may be better understood from the following detailed description, which is given by way of example and should be understood in conjunction with the accompanying drawings in which:

Fig. 1 is a block diagram of a wireless communication system according to the present invention;

FIG. 2 is a flowchart of an AP activation process according to an embodiment of the present invention;

FIG. 3 is a flowchart of an automatic channel selection process according to another embodiment of the present invention; and

FIG. 4 is a flowchart of an initialization channel selection process according to another embodiment of the present invention.

Detailed ways

Hereinafter, the term "WTRU" includes without limitation a user equipment (UE), a mobile station, fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment.

Hereinafter, the term "AP" includes without limitation an access point, a base station, a Node B, a node controller, or any other type of wireless environment interfacing device.

The features of the present invention can be incorporated into an IC or implemented in a circuit comprising multiple interconnected components.

As described below, the present invention is generally applicable to wireless local area network (WLAN) technologies, such as IEEE 802.11 and ETSI HyperLAN specifications in general, but it is conceivable to apply to other interference-limited wireless systems such as IEEE 802.15 and IEEE 802.16.

FIG. 1 is a block diagram of a wireless communication system 100 according to the present invention. The wireless communication system 100 includes an AP 105 and a plurality of WTRUs 110a-110n. AP 105 communicates with WTRUs 110a-110n over a wireless link 115 via an antenna 120. The AP 105 includes a transceiver 125 , a channel selector 130 , a measurement unit 135 , a power controller 140 , a timer 145 and a memory 150 . The transceiver 125 sends out signals 115a-115n to and receives signals 115a-115n from the WTRUs 110a-110n via the antenna 120.

Channel selector 130 selects a channel to communicate with each WTRU 110a-110n. Measurement unit 135 measures operational parameters supporting AP 105. The measurement unit 135 is responsible for collecting, processing, and storing channel measurement values. These measurement values include, but are not limited to: channel utilization (ie, the percentage of time the channel is busy), external (non-802.11) interference levels, received packets Measured received signal strength, and similar measurements. Power controller 140 controls the transmit power of AP 105. Timer 145 sets one or more predetermined periods during which AP 105 performs certain operations. Memory 150 provides storage capabilities for AP 105, including recording data such as measurement results.

2 is a flowchart of an AP 105 startup process 200 that includes a discovery step 210 and an announcement step 220. Within the discovery step 210, the AP 105 initializes its measurement parameters and values (step 211). The initialized measurement parameters and values may include, for example, the parameters and values listed in Table 1 below. As those skilled in the art will understand, other parameters and values may be used in addition to or substituted for these parameters and values.

symbol describe type Defaults ACS set of admissible channels configuration parameters {1, 6, 11} T _{mpp_fix} ^Discov Static measurement period yields the discovery step value for the fixed component of the interval configuration parameters 1000 milliseconds T _{mpp_va} ^Discov The discovery step value of the amplitude of the variable component of the static measurement period yield interval configuration parameters 0 milliseconds T _{mpp_du} ^Discov The discovery step value for the duration of a static measurement period configuration parameters 1000 milliseconds N _{MIN_} ^Discov Minimum number of measurement sets during the discovery step configuration parameters 4 N _{MAX_} ^Discov Maximum number of measurement collections during the discovery step configuration parameters 15 T _du ^Announ Notification step duration configuration parameters 10 seconds T _beacon ^Announ Beacon transmission period during the advertise step configuration parameters 100 milliseconds _Pmax Maximum AP transmission power configuration parameters 20dBm

Table 1

In step 212 of the discovery step 210, the measurement unit 135 measures operating parameters by performing N _{meas_sets} ^Discover measurement sets, thereby sequentially obtaining each channel in an admissible channel set (ACS) during a measurement set by implementing the The measured values within a period of time consisting of a complete cycle of the measurement period of all channels in the ACS. For example, the operating parameters may be AP 105 transmit power and channel settings. Preferably, the overall measurement duration (equivalent to T _{mpp — fix} ^Discover × N ^Discover ) on each channel is set such that strong enough packets are received from neighboring APs. Strong packets are packets that are sent at maximum power by an AP to increase their likelihood of being detected by neighboring APs.

The duration of T _{mpp_fix} ^Discover is set long enough to limit edge effects that occur when a packet is in transit during transitions between measurement periods (MPs). Also, it is preferable to set _{Tmpp_fix} ^Discover short enough to allow continuous rotation between channels so that AP 105 can detect a channel change in one of the neighboring APs. The duration and the period are determined by the timer 145 . The duration of the discovery step 210 consists of any number of measurement sets evenly distributed between N _{MIN_MS} ^Discover and N _{MAX_MS} ^Discover . The duration of the discovery step 210 is arbitrary, so as to consider the situation that two or more APs are powered on at the same time, and avoid these APs from performing preliminary channel selection at the same time.

Because of these measurements, the AP 105 is able to judge its radio environment, such as the detection of neighboring APs from its own ESS, the detection of neighboring APs from different ESSs, and the detection of external interference sources.

Referring back to FIG. 2 , upon completion of the N _{meas_sets} ^Discover performance measurement set (step 212 ), the power controller 140 initiates power control of the AP 105 (step 213 ). The power control determines a baseline range and an associated baseline power setting for the AP 105 . After the power control of the AP 105 has been initiated at step 213, the channel selector 130 initiates a channel optimization process (step 214) to select a channel to be used by a particular AP or network of APs. The preliminary channel settings for the AP 105 are determined based on parameters determined by the power controller 140 .

During the discovery step 210, the AP 105 remains silent (ie, the AP 105 does not send out any packets). After the discovery step 210 is complete, the AP 105 has collected enough information to determine a best operating channel and select a transmit power setting.

Following the discovery step 210 is a notification step 220 . During the advertising step 220 the AP configures its operating channel to the best channel decided at the end of the discovery step 210 . It should be understood that other processes may be performed during the transition as desired. The purpose of the advertising step 220 is to speed up the detection of an AP by its neighboring APs. At the beginning of the announcement step 220, parameters (eg T _dur ^Announce , T _beacon ^Announce , P _MAX ) are initialized (step 221 ). During the announcement step duration T _dur ^Announce , the AP 105 only sends out beacon frames with a maximum transmission power P _MAX at a period T _beacon ^Announce

(step 222). This speeds up the detection of the AP 105 by other APs since only maximum power packets are sent out. During the announce step 220, a WTRU outside the coverage of the AP 105 may attempt to contact the AP 105 because the AP 105 is transmitting at its maximum power _Pmax . Therefore, all contact requests from WTRUs may be denied during the advertise step 220 to avoid contacting a WTRU that would be out of range during normal operation.

Once the announcing step 220 is complete, the activation of the AP 105 is complete. The AP 105 then configures itself for its normal operation (step 223) and begins normal operation (step 230). AP 105 sets its transmit power to the setpoint determined by power controller 140, after which AP 105 begins normal operation and begins accepting contact requests from WTRU 110.

FIG. 3 is a flowchart of an automatic initialization channel selection process 300 according to an embodiment of the present invention. In the preferred embodiment, the channel selection process is initiated at the end of the discovery step 210, when measurements on each channel have been taken. Select the channel to be used by a specific AP or a network of APs. Channel selection may be done manually or automatically, and may be initiated at deployment or dynamically during operation. The invention may be implemented with wireless local area network (WLAN) applications (eg according to IEEE 802.11).

The initialization channel selection process 300 occurs during the start-up process 200 and determines the best operating channel. In a preferred embodiment, channels are scanned during the discovery step 210 . At the end of the discovery step 210 , the channel selection process is triggered in step 214 to select the best channel based on the measurements observed for each channel during the discovery step 210 . In all cases, the initialization channel selection process 300 scans multiple channels (eg, channels 1-11) to detect the best channel available. The sequence of scanned channels may be in a predetermined order, or it may be random. The channel sequence does not necessarily contain all available channels. For each scanned channel, the process determines: 1) what other APs are operating on that channel; 2) whether the AP is part of the same system (ie, by ESS); 3) the signal strength of the AP; 4) the amount of traffic on the channel; and 5) whether there are any other sources of interference (such as non-802.11 interference) on the channel, and the received non-WLAN interference power level. After the scan is complete, the AP can figure out which channel will get the best performance (eg, the channel with the least amount of interference). The AP will then retune itself to that channel. Depending on whether the other APs detected are part of the same system, the AP can decide to be more or less aggressive in the selection of the channel to use.

In an alternative embodiment, coordinated frequency selection can be accomplished by: 1) having the APs exchange information about their characteristics (such as load, capacity, or location); Centralized architecture of channels for all APs within the network. For the first case, each AP will still make the decision autonomously, but the information exchanged can allow a better decision (eg it may contain statistics that are difficult to be observed externally by another AP). For the second case, information is collected from different APs and communicated to a centralized unit or device which, after receiving the information, makes a decision and informs the different APs back of this decision.

Still referring to FIG. 3, when the initialization channel selection process 300 begins (step 305), the AP 105 is allowed to scan all channels to detect the identities of all nearby APs and a Received Signal Strength Indication (RSSI) (step 310). In a preferred embodiment, step 310 may be performed during discovery step 210 . In step 315, the channel list is scanned. All or a portion of the listed channels may be scanned sequentially in a predetermined or random order. Information associated with each AP detected for each channel is recorded (step 320). This information may include (but is not limited to) the identities of other APs operating on the channel being scanned, an indication of whether other APs are part of the same ESS, the signal strength of the AP, the amount of traffic on the channel, and whether there is any other sources of interference.

After the scan is complete, the AP 105 determines which channel provides the best performance (step 325). For example, this could be determined by measuring which channel has the least amount of interference or whether other APs are part of the same ESS. Once the channel with the best performance is determined, the AP 105 will tune itself to that best channel.

FIG. 4 is a detailed flow chart of an initial channel selection process 400 for determining the best channel after AP startup according to another embodiment of the present invention. The initialization channel selection process 400 includes a candidate channel determination process 405 and a channel selection process 450 .

In the candidate channel determination process 405, the AP 105 retrieves the maximum allowable interference _IMAX (step 410), which is the maximum allowable interference determined based on an AP's baseline range on any known channel. I _MAX can be derived from the power control process. Imax is calculated by the initialization channel selection process 400 using equation (1). Parameters used in Equation (1) Some of the parameters are retrieved from the power control process. Specifically, power control determines the RNG _base . On the other hand, P _max , (C/I) _{req_hig} and M ₁ are predetermined parameters. Preferably, I _MAX for the candidate channel decision process 405 is calculated according to equation (1):

I _MAX ＝P _max -RNG _base -(C/I) _{req_high} -M ₁ equation (1)

Wherein P _max is the maximum transmission power of the AP 105; RNG _base is the range covered by the AP 105; and (C/I) _{req_high} is the necessary carrier power-to-interference ratio of a high-rate packet (eg, 11 Mbps). _MI is a possible margin to eliminate the possibility that the channel has an interference level that is too close to the actual maximum allowable level. Another option is that a predetermined value of Imax is _IMAX used to determine the candidate channel list.

A first channel is selected from an ACS (step 415). The interference I of a channel is measured and compared with the maximum allowable interference I _MAX (step 420 ). If the interference I of the channel is less than the maximum allowable interference I _MAX , the AP 105 records the channel into a candidate list in the memory 150 (step 425 ). If the channel interference I is not less than the maximum allowable interference I _MAX , the AP 105 checks whether there are any channels in the ACS (step 430). If there are still channels in the ACS, the AP 105 selects the next channel from the ACS (step 435 ) and the candidate channel decision process 405 returns to step 420 .

If there are no more channels within the ACS, the AP 105 checks if there are any available candidate channels (step 440). If it is determined in step 440 that no candidate channel is available, the AP 105 increases I _MAX by ΔdB (step 445 ) and the candidate channel decision process 405 returns to step 415 . If it is determined in step 440 that at least one candidate channel exists, then the candidate channel determination process 405 is completed, and then the channel selection process 450 is performed.

One criterion used by the channel selection process 450 is the number N _B (k) of neighboring BSSs that have been measured on each channel. Once the candidate channel is selected, the minimum number N _B ^Min of detected beacons from different BSSs among all the candidate channels is determined (step 455 ). The number of neighboring BSSs measured on channel k is N _B (k) and the minimum number of measured BSSs is N _B ^Min for comparison and removed from the list of candidate channels $N_B\left(k\right)>N_B^{\mathrm{Min}}$ All channels of (step 460). In other words, only channels with the least measured BSSs are left. Alternatively, in steps 455 and 460, the number of measured neighboring BSSs on each channel may be exchanged for the channel usage on each channel. The channel utilization measurement corresponds to the percentage of time the receiver is carrier locked to a WLAN signal. In this case, the channel selection process would favor the channel with lower channel usage.

Another criterion used in the channel selection process is the minimum measured interference level, which is determined from all remaining candidate channels (step 465). The minimum measured interference level I(k) on channel k is compared with the minimum interference level I _MIN , and all channels with I(k)>I _MIN are removed from the candidate channel list (step 470 ). In other words, only channels with minimal interference levels are left.

If more than one minimum power level candidate channel exists, a channel is randomly selected among the remaining candidate channels (step 475).

Example parameters to initiate the channel selection process 400 are listed in Table 2 below. Those skilled in the art will understand that other parameters and values may be used in addition to or substituted for these parameters and values.

symbol describe type Defaults ACS set of admissible channels configuration parameters {1, 6, 11} N _B (k) The number of neighboring BSSs measured on channel k. Neighboring beacon frames are detected using the minimum value of EDT. measured value none I(k) Interference measured on channel k. I is measured as the average received signal power when the receiver is not "carrier locked" (ie, the receiver is not receiving any packets). measured value none RNG _base Baseline range (set by path loss discovery process internal parameters none Certainly) (C/I) _req The minimum necessary carrier power-to-interference ratio to support the maximum data transmission rate configuration parameters 10dB _Pmax Maximum AP transmission power configuration parameters 20dBm I _MAX The maximum allowable interference on any known channel determined based on the baseline range internal parameters none _MI The interference margin used for the calculation of the maximum permissible interference level I _MAX configuration parameters 3dB △ The amount to increase the maximum permissible interference I _MAX when there is no candidate channel with I < I _MAX , in dB. configuration parameters 3dB

Table 2

Although the features and components of the present invention have been described in particular combinations in preferred embodiments, each feature or component can be used alone or in various combinations with or without other features and components of the present invention.

Claims (6)

1. the method selected of the employed channel of an optimization access point said method comprising the steps of:

Decision is the basis with the baseline scope of said access point on any known channel maximum is allowed and is disturbed I _MAX, I wherein _MAX=P _Max-RNG _Base-(C/I) _{Req_high}-M _I, P _MaxBe the maximum transmission power of said access point, RNG _BaseBe the scope that said access point covers, (C/I) _{Req_high}Be the necessary carrier power interference ratio of two-forty package, M _IBe to eliminate to possess too near I _MAXThe enough and to spare of channel of interference level, make the interference level and the I of channel _MAXBetween difference can be less than M _I

Select to supply the candidate channel of said access point use, wherein the interference of selected candidate channel is less than I _MAXAnd

In the middle of said candidate channel, select a channel based on the channel choice criteria, wherein select a channel to comprise:

The quantity of decision beacon of detecting on each said candidate channel and select at least one to possess the said candidate channel of the said detecting beacon of minimum number; Or

Determine the interference level of said candidate channel and select at least one to possess the said candidate channel of least interference level.

2. method according to claim 1 is characterized in that, said candidate channel is to be selected from the tolerable channel set.

3. method according to claim 1 is characterized in that, also comprises step:

When having two to select candidate channel, select a candidate channel at least randomly.

4. an access point comprises:

One measuring unit, the maximum that is the basis through the baseline scope that is configured to determine on any known channel with said access point are allowed and are disturbed I _MAX, I wherein _MAX=P _Max-RNG _Base-(C/I) _{Req_high}-M _I, P _MaxBe the maximum transmission power of said access point, RNG _BaseBe the scope that said access point covers, (C/I) _{Req_high}Be the necessary carrier power interference ratio of two-forty package, M _IBe to eliminate to possess too near I _MAXThe enough and to spare of channel of interference level, make the interference level and the I of channel _MAXBetween difference can be less than M _I

One channel selector, through being configured to select to supply the candidate channel of said access point use, wherein the interference of selected candidate channel is less than I _MAXAnd

Said channel selector, also through being configured in the middle of said candidate channel, to select a channel based on the channel choice criteria, said channel choice criteria comprises the detecting beacon or a least interference level of a minimum number.

5. method according to claim 4 is characterized in that, said channel selector is used for from the said candidate channel of the incompatible selection of tolerable channel set through configuration.

6. method according to claim 4 is characterized in that, said channel selector is selected said channel randomly through being configured to when existing at least two to select candidate channel in the middle of said candidate channel.

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