MXPA06007743A - Method for clear channel assessment optimization in a wireless local area network - Google Patents

Abstract

A method for optimizing clear channel assessment (CCA) parameters in a wireless local area network having an access point (AP) and at least one station begins by receiving a trigger condition. An upper bound and a lower bound for an energy detect threshold (EDT) parameter are determined. A value of the EDT parameter is calculated and is bound by the upper bound and the lower bound. Lastly, the EDT parameter is updated. The method can be performed at each station or at the AP, with the updated CCA parameters being signaled to each station associated with the AP.

Description

METHOD FOR OPTIMIZATION OF ESTIMATION OF QUANTITATION OF CHANNELS IN A WIRELESS NETWORK OF LOCAL AREA FIELD OF THE INVENTION The present invention relates, in general, to wireless local area networks (WLANs), and more particularly, to a method for optimizing the channel vacancy estimation parameters in a WLAN.

BACKGROUND In WLAN systems, the Distributed Coordination Function (DCF) is the fundamental access method for asynchronous data transfer based on the best effort. The WLAN DFC mode is used to support containment services that promote satisfactory access to the channel for all stations. The multiple access scheme used to achieve this is Access. Multiple by Carrier Detection Avoiding Collisions (CSMA / CA). One way through which stations detect if the channel is busy is to analyze all the detected packets that are sent from other WLAN users and detect the activity in the channel by means of the relative signal strength from other sources. The physical detection of the carrier that is carried out before the transmission of data is called Channel Unemployment Estimate (CCA).

"The CCA is used for the transmission and reception of packets in 802.11 devices, before the transmission of data, the device must ensure that the wireless medium is free, using CCA." For the reception of data, the device only detects packets that meet the CCA criteria for a busy channel 802.11 standards define different CCA modes A commonly used CCA mode requires carrier detection and energy greater than the Energy Detection Threshold (EDT) before reporting More specifically, the CCA reports on a medium occupied after the detection of a WLAN signal type with power greater than the EDT Other CCA modes require only carrier detection, or energy greater than the EDT only. Individual EDT is typically used to tune the CEC for both transmission and reception packets.The CCA is well tuned to t Transmissions when: 1) The access point (AP) always detects the channel as busy when a station (STA) of its basic service set (BSS.) is transmitting a packet. 2) The AP always detects the channel as busy when the STA to which it has to send a packet also detects the channel as busy due to a transmission of packets from a device in a neighboring BSS. When fulfilling this condition, the AP postpones external packets that would produce transmission errors. 3) The AP always detects the channel as free when the STA to which it has to send a packet detects the channel as free, even if a device of a neighboring BSS is using the channel. By fulfilling this condition, unnecessary postponements are avoided. On the other hand, the CCA is well tuned for, reception when: 1) The AP capable of receiving packets from all STAs within the coverage area of your BSS. If the EDT parameter is set too high, the AP may not receive packets that are transmitted by an STA located at the edge of the cell. 2) The AP does not detect packets from devices in Neighboring BSSs If the EDT parameter is set too low, the AP could "block the carrier" on packets that are transmitted by STAs that are located outside their BSS or that are transmitted by other APs. When "locked" in external transmissions, the AP will lose any transmission from an STA of its own BSS. Such a scenario would result in a packet error, since the STA packet from its own BSS would collide with the external packet that the AP is receiving. The determination of the ideal EDT configuration implies a balance between optimization for packet transmission and optimization for packet reception. In addition, a dynamic method is required to adjust the EDT parameter, in order to adapt to various network conditions (for example, a change in the size of the BSS).

The invention Three methods are described for optimizing the CCA parameters in a WLAN having an access point (AP) and at least one station without AP (STA). The term "CCA parameters" is used herein to collectively designate the CCA mode and the value of the EDT parameter. The first method does not require any specific signaling between the STAs, or between an STA and an AP. In this method, each STA or AP tries to independently find the optimal configuration for its CCA parameters based on certain statistics. The STAs and the AP do not share information regarding the configuration of the CCA parameters. This method begins by receiving an activation condition. An upper limit and a lower limit for the EDT parameter is determined. A value of the EDT parameter is calculated, which is limited by the upper limit and the lower limit. Finally, the EDT parameter is updated. The method can be carried out in any of the STAs, all the STAs, or in the AP. The second method requires signaling between STAs or between an STA and an AP, to communicate the CCA parameter values used by the STAs or the AP. In this method, each node (STA or AP) has the possibility to know the values of the CCA parameters used by other STAs or the AP, but a node can only modify its own CCA parameters. This second method begins with an order from an STA or AP to other STAs and / or the AP to report the values of the CCA parameters currently used. The requested STAs and / or AP report these values to the STA or to the requesting AP. Then, the requesting AP or AP computes the optimal values to be used with its own CCA parameters. After this computation, the requesting AP or STA can change the values of its own CCA parameters and, optionally, signal the new values to other STAs or to the AP. The third method requires signaling between STAs or between an STA and an AP, which allows an STA or AP to modify the values of the CCA parameters used by other STAs or the AP. In this third method, a node can determine the optimal configurations of the CCA parameters for themselves, as well as for other nodes in system 1, and can request that other nodes use their respective optimal CCA parameters, as determined by the requesting node. In a BSS of the infrastructure comprising an AP and one or more STAs, the requesting node should preferably be the AP. This method begins when the AP calculates the optimal CCA parameters for one or multiple STAs associated with the AP. This calculation may (or may not) be equal to the calculation used in the first method. After the determination of the optimal CCA parameters for each STA, the AP indicates the respective values of the optimal CCA parameters for each STA. The STAs determine if the requested parameter change is possible and indicates the success or failure of the change in a response message to the AP. An access point for optimizing CCA parameters in a wireless local area network having at least one station comprises a receiver, an energy detector, a channel availability determination device, and a CCA calculation device that receives parameters input from the access point and calculates the CCA parameters. A station for optimizing CCA parameters in a wireless local area network having an access point comprises a receiver, an energy detector, a channel availability determination device and a CCA calculation device that receives input parameters from the station and calculate the CCA parameters. An integrated circuit to optimize the CCA parameters in a wireless local area network comprises a receiver, an energy detector, a channel availability determination device, and a CCA calculation device that receives input parameters and calculates the parameters CCA.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood through the following description of a preferred embodiment, given by way of example and to be interpreted together with the accompanying drawings, in which: Figure 1 is a flow diagram of an optimization procedure of energy detection threshold according to a first method of the present invention; Figure 2 is a block diagram of an apparatus incorporating a method embodiment shown in Figure 1; Figure 3 is a diagram showing the signaling between an AP or STA and another AP or STA for implementing a second method according to the present invention; and Figure 4 is a diagram showing the signaling between an AP and an STA to implement a third method according to the present invention.

DESCRIPTION OF THE PREFERRED MODALITY The present invention describes methods for dynamically optimizing the EDT parameter that is used for. CCA in WLAN systems. Table 1 - Definitions of parameters Table 1 - Definitions of parameters Figure 1 presents a flowchart of an optimization method of CCA 100 using a first method according to the present invention. The procedure 100 can be applied both in the AP and in individual STAs. This CCA optimization procedure directs the determination of the appropriate level of the EDT. The CCA mode is preferably set so that it indicates that it is busy if the received signal is higher than the EDT and a WLAN signal is detected. Alternatively, the CCA mode can be set to indicate that it is busy if the received signal is greater than the EDT only.

Activation The EDT 100 optimization procedure is activated with any of the following conditions: 1 PERTx > PERTxMAX and at least NTx packets have been transmitted since the last EDT update. 2. PERRx > PERR¡? X and at least NRX packages have been received since the last EDT update. 3. Expiration of a periodic activation timer, ie Telapsed > Tperiodic, and at least Ntx packets have been transmitted and at least NRx packets have been received since the last EDT update. Teiapsed is the time since the last EDT update. When activated in accordance with condition 1, the optimization procedure 100 attempts to solve the problem of insufficient postponement. One cause of excessive packet errors in the downlink (DL) is an EDT configuration that is too high, the AP does not detect the channel as busy while the STAs block the carrier in transmissions from the neighboring BSS, a minimum number of packets is imposed transmitted to ensure that the problem really exists.When activated according to condition 2, the optimization procedure 100 attempts to solve the highly sensitive AP problem.A cause of excessive packet errors in the uplink (UL) is a configuration of the EDT is too low, the AP is blocked in neighboring BSS packets, causing the loss of packets from their own STAs.A UL packet error occurs, generally, when a STA transmits a packet while the AP has already blocked the carrier in a transmission from the neighboring BSS, a minimum number of received packets is imposed to ensure that the problem actually exists, condition 3 is for an optimized general The optimization procedure 100 is activated periodically, once transmitted and received enough packets to collect significant statistics. The activation parameters must be selected so that the optimization procedure 100 reacts quickly to a situation of excessive packet errors. For example, the optimization procedure 100 could be activated periodically once per second, once sufficient statistics have been collected. If a minimum of 100 packages is required for activation, an error rate of 10% results in 10 errors.

Determination of EDT limits The optimization procedure 100 starts by determining an upper limit and a lower limit for the EDT parameter (step 102). An upper limit on the EDT, ED MAX parameter is determined as follows: EDTMAX = PStñ- (R ^ Gbase + RNGadj) Equation (1) where RNGadj is a range adjustment value determined by the power control algorithm. The EDT parameter must be set so that the AP can at least detect all packets that originate from its own BSS. EDTmax corresponds to the level of signal in which a transmission is received from an STA located at the edge of the cell. The calculated value of EDTM? X is compared to the maximum value allowed by the 802.11 standards, and the smaller of the two values is taken. The maximum EDT value allowed by the standard is based on the transmission power of the AP, PAP. EDTMAX is dynamically calculated as RNGbase, RNGadj and PSTA can be modified by means of the Power Control algorithm at any time, and is updated whenever there is a modification of RNG to Ser RNGadj and PSTA- 'The lower limit in the EDT parameter, EDTMIN is set at the sensitivity level of the AP receiver, RSñP.

Updating the EDT Then, the EDT parameter is calculated based on its current value, the received and transmitted packet error rates and the postpone speed (step 104): The default value for the weighting factors is 1 and can be optimized based on system utilization (ie, the arrangement of APs and STAs). The EDT parameter is set between the upper and lower limits (step 106): EDT: = max (£ TMXW, min (EDTHM, EDT)). : Equation (3) The EDT value is updated (step 108) and the procedure ends (step 110). It should be noted that if a channel change occurs since the last invocation of the EDT 100 optimization procedure, the EDT parameter is automatically set to EDTmN. Alternatively, it is possible to use different EDT parameter settings for transmission and reception. EDTT? is optimized for packet transmission, while EDTR? it is optimized for the reception of packages.

Immediately before sending a packet, the AP sets the CCA EDT parameter in EDTTX and sets it back to EDTRX once the data transmission is complete. The EDTT? it is determined using a procedure similar to the one shown in Figure 1, except for the use of the following equation: EDTTX is then adjusted between the upper and lower limits, as shown in Equation (3). In one modality, EDT? = RNGbase- In another modality, EDT? it is fixed according to the following equation: Equation '(5) Figure 2 shows an AP or an STA 200 that is constructed in accordance with the present invention. The AP or the STA 200 includes a receiver 202 connected to a power detector 204. A channel availability determination device 206 is connected to a power detector 204 and a CCA calculation device 208 is connected to a power device 208. determining the availability of channel 206. The CCA 208 computing device accepts parameters, such as DR and PER, as inputs and outputs an EDT value to the availability determination device of channel 206, which uses the EDT value to determine whether the channel is busy.

The value 'EDT is also repeated again to the CCA calculation device 208 and used as shown in Equations 2 and 3. Figure 3 shows a diagram of a CCA 300 optimization procedure using the second method. This method can be used by any STA or AP. The STA or the AP using the method is referred to as "optimization" station 302. The optimization station 302 requests information about the configuration of the CCA parameters in other STAs or AP 304 (step 310). There are several possibilities to implement this signaling. The first possibility is for the optimization station 302 to send separate requests (unicast) to each surrounding STA or AP 304 ("requested stations") whose addresses are known to the optimization station 302. The optimization station 302 can know these addresses to through different means. For example, if the optimization station 302 is an AP, it necessarily knows the addresses of all the STAs associated with it. If the optimization station 302 is an STA, it can know the addresses of other STAs in the same basic service set (BSS) by observing the MAC addresses of received packets. However, the WLAN protocol may not allow direct communication between STAs in a BSS of the infrastructure. In that case, this method would be used by the AP only.

The order must contain the addresses of the optimization station 302 and the requested station 304. In an 802.11 WLAN, this information would already be in the MAC header. Optionally, the request may contain a time limit for the requested station 304 to respond. The requested station 304 again sends a confirmation immediately after the correct reception of the package containing the order (as well as any other packet addressed to a specific station). In this way, the optimization station 302 knows that the requested station 304 has received the order in an appropriate manner, and can retransmit the package containing the order if it did not receive a confirmation after a certain time. A second possibility is that the optimization station 302 sends a general request directed to all the surrounding stations 304. This can be carried out by transmitting a broadcast message specifying only the identity of the basic service set (BSS), in which case they would only respond the STAs that belong to the specified ESS. This can also be done by transmitting a multicast message that specifies the addresses of all STAs from which you want to obtain a report on IQS CA parameters. In a third possibility, an STA (without AP) can request the AP with which the CCA parameters of one or more STA (s) associated with this AP is associated, instead of directly requesting the parameters to the STA. This request would contain the address of the STA (s) from which you want to have a report of the CCA parameters, or a special indicator that indicates that the CCA parameters of all the STAs in the BSS are requested. After this request, the AP can respond with the CCA parameters of the requested stations 304. The AP can already have this information, or it may need to request the information (using one of the mechanisms described above) from the STAs before responding to the optimization station 302. For any STA that successfully receives an order of CCA parameters according to one of the mechanisms described above, the STA reads the values of the CCA parameters it is currently using (step 312). These values (CCA and EDT mode) can normally be found in the management information base (MIB) of the requested station 304. Once the CCA parameters have been read, the requested station 304 (after gaining access to the medium according to the protocol 802.11 usual) transmits a report on CCA parameters (step 314). This report can be a broadcast to all the STAs in the BSS (in which case a confirmation is not expected) or, preferably, it can be a unicast addressed to the optimization station 302. In the latter case, a confirmation is expected from the station 8 optimization 302 and the requested station 304 can retransmit in case of failure. The report contains the values of the CCA parameters. Once the optimization station 302 has received reports on CCA parameters from all the requested stations 304 (or after a certain period of time elapses since the transmission of the orders, at the will of the optimization station 302), the optimization station 302 calculates the new CCA parameters that it will use for itself (step 316). A simple method for determining CCA parameters is to use those from the most sensitive STA from which the CCA parameters were received (ie the STA with the lowest configuration of the EDT parameter). If information on path loss is available, the EDT parameter can be calculated as sensitive as the more sensitive reporting STA. For example, an AP can set its EDT parameter so that it is as sensitive to external transmissions as is its STA more sensitive. The AP can achieve this by setting its EDT parameter lower than the EDT parameter of the more sensitive STA by an amount equal to the difference of path losses to the most dominant external interferences. Once the optimization station 302 has calculated the new CCA parameters that it should use, it can immediately apply the new configuration. Optionally, you can send a CCA parameter notification to other requested stations 304 to inform them about the new configuration now used by the optimization station 302 (step 318). This message can be directed to specific STAs (unicast) or multiple STAs (multicast or broadcast). Figure 4 shows a 'diagram of a CCA 400 optimization procedure using the third method. This method is preferably used by the AP in a BSS of the infrastructure, although use by a station without AP is not excluded (for example in a separate BSS). • The AP using the method is called "controlling" station 402. The controlling station 402 computes or estimates the optimal CCA parameters for itself and other STAs in the same BSS ("controlled" stations 404, step 410). This determination can be carried out or not using the method 100 that has been disclosed above. Once the optimal CCA parameters have been determined for each? TA (these may or may not be different from a controlled station 404 to another dependent on the algorithm), the controlling station 402 requests the controlled stations 404 to modify their CCA parameters ("control request"). of CCA parameters "step 412). If the CCA parameters are the same for all the controlled stations 404, the controlling station 402 may transmit a broadcast message containing the BSS identity together. with the values of the CCA parameters, and optionally a time limit to respond. It can also transmit a multicast message containing the addresses of all the controlled stations 404 together with the values for the CCA parameters. Preferably, the controlling station 402 transmits a unicast message (with acknowledgment) separately to each controlled station 404 with its new CCA parameters. When the new CCA parameters are different from one controlled station 404 to another, multicast or unicast messages are required. Upon successful receipt of the CCA parameter control request message, a controlled station 404 determines whether it is possible to apply the new CGA parameters requested by the controlling station 402 (step 414). The application of the new parameters may not be possible, depending on the capabilities of the controlled station 404 (for example, radiosensitivity or the availability of the requested CCA mode). If the modification is possible, the controlled station 404 immediately modifies its CCA parameters (step 416) and transmits a response ("CCA parameter control response") as a unicast message to the controlling station 402 (preferred) or as a broadcast message to all STAs in the BSS (step 418). This message contains an indicator that indicates the success or failure of the modification of the CCA parameters.

In case of failure, the message may optionally contain a "cause" field that specifies the reason for failure (such as CCA mode not available or EDT value requested too low or too high). It can also contain the values of the CCA parameters currently in use by the controlled station 404. After receiving the responses from all the controlled stations 404 (or after a certain period of time has passed since the transmission of the orders, at the will of the station controller 402), the controlling station 402 may decide to do nothing until the next programmed activation of the optimization algorithm, in a manner similar to that described in method 100. The controlling station 402 may also decide to repeat the transmission of orders to the controlling stations 404 in case some of them did not transmit a response again. While the present invention is described herein in relation to a WLAN, the principles of the present invention can be applied to other types of wireless communication systems. In such circumstances, the STA could include, but not be limited to, devices such as a wireless transmit / receive unit (WTRU), a user equipment, a fixed or mobile subscriber unit, a pager or any other type of device capable of operating in a wireless environment. Likewise, the AP may include, without being limited to, devices such as a base station, a Node B, a site controller, or any other type of interface device in a wireless environment. While the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone (without the other features and elements of the preferred embodiments) or in various combinations with or without other features and features. elements of the present invention. While specific embodiments of the present invention have been shown and described, many modifications and variations may be made by one skilled in the art without departing from the scope of the invention. The above description serves to illustrate and in no way limit the particular invention.

Claims (25)

1. CLAIMS 1. Method for optimizing channel vacancy estimation parameters in a wireless local area network having an access point (AP) and at least one station, the method is characterized in that it comprises the steps of: receiving a condition of activation; determine an upper limit and a lower limit for an energy detection threshold (EDT) parameter; calculate the value of the EDT parameter; limit the EDT parameter by the upper limit and the lower limit; and update the EDT parameter. Method according to claim 1, characterized in that the activation condition exists when an error rate of transmitted packets exceeds a target maximum transmitted packet error rate and a minimum number of packets have been transmitted. Method according to claim 1, characterized in that the activation condition exists when an error rate of received packets exceeds an error rate of maximum received received packets and a minimum number of packets have been received. Method according to claim 1, characterized in that the activation condition exists when a minimum period of time has elapsed, a minimum number of packets have been transmitted and a minimum number of packets have been received. 5. Method according to claim 1, characterized in that the upper limit is determined by the formula: EDTwx -.P¿ "- t? MS 4" '+ RNGad1), where P? T? Is the power of station transmission, RNGbse is a baseline range of the AP, and RNGadj is a range adjustment value 6. Method according to claim 1, characterized in that the lower limit is equal to the sensitivity level of the receiver of the station. AP 7. Method according to claim 1, characterized in that the calculation step consists of calculating the value of the EDT parameter through the formula: where PERRX is an error rate of received packets, PERRX "2 ^ is an error rate of maximum received packets, PERTX is an error rate of transmitted packets, PERT? mx is an error rate of transmitted packets maximum objective , DR is a deferral velocity, DF? 1 ^ is a target maximum deferral velocity,? Is a step size value, ya,? E? Are weighting factors 8. Method according to claim 1, characterized because the calculation step consists in calculating a "value of EDT transmission and an EDT reception value. Method according to claim 8, characterized in that the EDT transmission value is calculated by the formula: ED ?? X = EDTn and D. ß X PFYRJy x J where DR is a deferment speed, DR "1 ^ is a maximum target deferment speed, PERTX is an error rate of transmitted packets, PERTX is a maximum target transmitted packet error rate,? is a value of the size of step e and ß are weighting factors 10. Method according to claim 8, characterized in that the EDT reception value is equal to a base line range of the AP. with claim 8, characterized in that the EDT reception value is calculated through the following formula: EDT ^ = EPT ^ a -a -? ^ "-where EDTMAX is a maximum EDT value, PERR, is an error rate of received packets, PERR? Mx is an error rate of maximum received received packets, and is a weighting factor 12. Method according to claim 1, characterized in that the method is carried out in each station 13. Method according to claim 1, characterized in that the method is carried out in the AP and <;% 1 updated EDT parameter is signaled to each station associated with the AP 14. Method of compliance with claim 13, characterized in that the updated EDT parameter is signaled individually to each station associated with the AP 15. Method of compliance with claim 13, characterized in that the updated EDT parameter is broadcast simultaneously to all the stations associated with the AP. 16. Method for optimizing channel vacancy estimation parameters (CCA) in a wireless local area network having an optimization station and a requested station, the method is characterized in that it comprises the steps of: sending an order of CCA parameters from the station, optimization to the requested station; read the CCA parameters at the requested station; report the CCA parameters of the requested station to the optimization station; and compute new CCA parameters in the optimization station. Method according to claim 16, further characterized in that it comprises the step of: notifying the requested station of the new CCA parameters. Method according to claim 16, characterized in that the optimization station is an access point; and the station requested is at least one station. Method according to claim 16, characterized in that the optimization station is an access point; and the requested station is an access point. Method according to claim 16, characterized in that the optimization station is a station; and the station requested is at least one station. 21. Method according to claim 16, characterized in that the optimization station is a station; and the requested station is an access point. 22. Method for optimizing channel vacancy estimation parameters (CCA) in a wireless local area network having an access point (AP) and at least one station, the method is characterized in that it comprises the steps of: calculating CCA parameters optimal for a station in the AP; send a CCA parameter control request from the AP to the station; determine if the station can change to the required CCA parameters, and change the CCA parameters in the station if the change can be made; and respond to the CCA parameter control request by sending a message from the station to the AP. 23. Access point for optimizing parameters for channel vacancy estimation (CCA) in a wireless local area network having at least one station, such access point is characterized in that it comprises: a receiver, an energy detector; channel availability determination device, and a CCA calculation device that receives input parameters from that access point and calculates the CA parameters. 24. Station to optimize parameters of channel vacancy estimation (CCA) in a wireless network of local area having an access point, such a station is characterized in that it comprises: a receiver, an energy detector, a channel availability determination device, and a CCA calculation device that receives input parameters from such station and calculates the CCA parameters 25. Integrated circuit to optimize channel vacancy estimation parameters (CCA) in a network in wire of local area, characterized in that it comprises: a receiver; an energy detector; a device for determining the availability of the channel; and a CCA calculation device that receives input parameters and calculates the CCA parameters.