KR200422108Y1 - Apparatus for generating loud packets to estimate path loss - Google Patents

Abstract

In a wireless communication system (e.g., a WLAN) comprising a plurality of wireless transmit / receive units (WTRUs) and a coordinating node (e.g., an access point (AP)), packet loss is the first WTRU in the WTRU. Is estimated by sending a loud packet from the WTRU to the second WTRU The coordinating node sends a loud packet generation request message The first WTRU receives the loud packet generation request message and transmits specified by the loud packet generation request message Transmit at least one loud packet at power Optionally, the first WTRU sends the loud packet generation response message The second WTRU receives the loud packet and the signal strength of the loud packet from the determined transmit power of the loud packet And subtract the path loss between the first WTRU and the second WTRU.

Description

Apparatus for generating a loud packet to estimate path loss {APPARATUS FOR GENERATING LOUD PACKETS TO ESTIMATE PATH LOSS}

1 is a flow signal diagram in which loud packets are sent from a coordinating node to one or more WTRUs in a wireless communication system constructed in accordance with the present invention.

2 is a block diagram of a wireless communication system including a plurality of WTRUs using smart antennas to transmit and receive loud packets according to the present invention.

3 is a flow diagram of a process for estimating path loss between two WTRUs in accordance with an embodiment of the present invention.

4 is a flow diagram of a process of estimating a path loss between two WTRUs based on information included in a loud packet generation request message sent by a coordination node according to another embodiment of the present invention.

5 is a flow diagram of a process of estimating a path loss between two WTRUs based on conditions specified by a loud packet generation request message sent by a third WTRU in accordance with another embodiment of the present invention.

The present invention relates to a wireless communication system (eg, a wireless local area network (WLAN)) comprising a plurality of wireless transmit / receive units (WTRUs) (ie, mobile stations). A method and apparatus for generating a loud packet to estimate path loss between WTRUs.

In a wireless system where a multi-access scheme is based on carrier sense multiple access / collision avoidance (CSMA / CA) according to the IEEE 802 standard (e.g., IEEE 802.11), the WTRU Determine when to attempt to transmit and receive a packet based on the reception strength of a signal transmitted from a neighboring WTRU using the same channel. By avoiding simultaneous transmissions, multiple WTRUs can avoid interfering with each other while sharing the same channel.

WTRUs typically use several important variables, such as energy detect threshold (EDT) and defer threshold (DT), to determine when packets can be sent and received. EDT represents the minimum received signal power at which packet reception is attempted. DT represents the minimum received signal power at which packet transmission by the WTRU is delayed. The DT value may or may not be the same as the EDT value.

Although the basic concept of CSMA / CA may not be direct, there are certain situations that result in excessive capacity reduction relative to the maximum capacity that can be achieved. For example, there are cases where two transmitters (communicating with different receivers) can transmit simultaneously without significant interference with each other, but they do not because they can recognize more than their respective EDT and / or DT values from each other. This results in capacity loss that can be avoided if the following measures are taken:

a) WTRUs cannot recognize each other beyond EDT (and / or DT), but reduce their transmit power so that they can still communicate with each other at the optimum data rate;

b) WTRUs increase their EDT (and / or DT) such that the signals they receive from each other are below a threshold; or

c) a combination of a) and b).

The technique by which a node or a system determines and sets the aforementioned variables (transmission power, EDT, DT) is referred to as deferral management hereinafter. Proper setting of these variables will be done if the WTRU knows not only the path loss between them, but also the EDT or DT values used by other WTRUs. This knowledge means that the WTRU (or another node, such as an access point (AP) that controls some variables of the WTRU), determines whether a received signal by transmission at a particular level is above or below the EDT of that neighboring WTRU. Make it predictable. This knowledge can then be used in algorithms to optimize capacity.

Obtaining a path loss estimate is also useful for positioning purposes. Using the knowledge of the location of some fixed WTRUs (typically, APs or mesh points (MPs in the mesh network)), as well as the knowledge of the establishment of path loss between WTRU pairs, the location of the WTRUs can be estimated This estimation may be performed by a node (whether or not a WTRU) collecting path loss estimates from one or several other WTRUs.

Thus, there is a desire for a WTRU to reliably estimate path loss with other WTRUs.

Problems to Resolve

The direct way in which the first WTRU can estimate the path loss between itself and an adjacent second WTRU is to subtract the received power it perceives from the transmit power used by the second WTRU. This assumes that the first WTRU can determine the signal it measured and can determine the power that the second WTRU transmits. The reason why this is not possible in the current WLAN technology is as follows.

1) In current technology WLAN, the setting of transmit power by AP, WTRU and MP is proprietary and does not communicate with other WTRUs. For example, current 802.11h / 802.11k transmission power control (TPC) mechanisms impose a maximum transmission power setting on a basic service set (BSS) that is not exceeded for regulatory purposes. It should be understood that any WTRU may change its transmit power below its maximum imposition limit without communicating its inherent proprietary decisions with other WTRUs, APs, or MPs.

2) The transmit power used by each WTRU may vary on a packet basis. This will receive a packet from the second WTRU to estimate the path loss that the first WTRU separates it from the second WTRU, so that the power to which the packet was sent will be indicated in the packet. Using the same example described above, the only signaling that allows such a packet to be sent is an 802.11h / 802.11k TPC request / TPC report frame exchange mechanism that requests a dedicated bidirectional signal exchange and cannot be established periodically. frame exam mechanism). In addition, TPC requests / reports cannot be sent to WTRUs outside of the BSS. In one scenario, the WTRU adjusts its transmit power and DT / EDT variables to increase the capacity of the system without creating hidden nodes within and across the system's BSS, resulting in loss of path between the WTRUs from other WTRUs. Knowledge is often desired.

3) In various scenarios, the first WTRU may not be aware of the second WTRU because the second WTRU transmits at a power lower than the maximum power of the first WTRU. This may be the case when the second WTRU uses battery management techniques or delay management techniques. In a scenario where the WTRU aims to adjust its delay management variable, it would be desirable to estimate the path loss of the WTRUs even if the WTRUs cannot be recognized. There is currently no way for a WLAN node instructing another WLAN node to increase its transmit power, or even command the use of a particular transmit power other than specifying the maximum power that can be used. This also applies to the TPC request / TPC report described above.

The above discussion of supporting path loss between WTRUs with or without the mechanism has several problems. In some cases, the mechanism allows the WTRU to estimate the transmit power value of the neighboring WTRU, which is not very precise when there is variation between different WTRU manufacturers and the neighboring WTRU uses a transmit power lower than the maximum. In other cases, any path loss estimation between two WTRUs can be completely prevented from being performed.

The present invention is implemented in a wireless communication system that includes a number of WTRUs and a coordinating node (eg, an access point (AP)). The loud packet is sent from the first WTRU in the WTRU to the second WTRU. The coordinating node sends a loud packet generation request message. The first WTRU receives a loud packet generation request message and sends at least one loud packet at the transmit power specified by the loud packet generation request message. Optionally, the first WTRU sends a loud packet generation response message. The second WTRU receives the loud packet and determines the path loss between the first WTRU and the second WTRU by subtracting the signal strength of the loud packet from the determined transmit power of the loud packet.

The invention will be more fully understood from the following detailed description, which is provided by way of example and is understood in conjunction with the accompanying drawings.

In the following, a WTRU includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other kind of device capable of operating in a wireless environment. Do not. In the following, an access point (AP) includes, but is not limited to, a Node B, a site controller, a base station or any other kind of interface device in a wireless communication environment.

In the following description, a WTRU is defined as any node in a wireless communication system (e.g., an IEEE 802 WLAN system) and a station (AP or non-independent basic service set) or infrastructure BSS in an infrastructure BSS. (non) -AP), or mesh point, mesh AP, or mesh portal within a mesh network.

A feature of the present invention may be integrated with an integrated circuit (IC) or composed of a circuit comprising a plurality of connection elements.

Loud  packet concept

According to one embodiment of the present invention, the WTRU sometimes transmits packets with high transmission power (hereinafter referred to as loud packets), and thus the values at which the packets are transmitted are known to other WTRUs. These loud packets need not be directed to any particular WTRU or WTRU group, but simply broadcast to a set of WTRUs receiving on the same frequency channel. A neighboring WTRU wishing to estimate its path loss for the WTRU transmitting the loud packet may do so by simply comparing the signal strength of the received loud packet with the indicated or known transmit power of the loud packet. For example, the path loss estimate can be obtained using the following equation.

Path Loss (dB) = Transmission Power of Loud Packet (dBm)-Received Signal Strength of Loud Packet (dBm) Equation (1)

Preferably, the transmit power of the loud packet is indicated in the loud packet itself as an information field. In addition, such transmit power may be broadcast periodically by the AP, directed to each WTRU in association with the AP, or communicated to the WTRU as part of another signal exchange. In this case, there is an information field present in the loud packet for indicating a receiving WTRU, which is a loud packet and is not a normal packet. Preferably, the transmit power of the loud packet should be equal to the maximum transmit power of the WTRU transmitting the loud packet. This ensures the widest possible area for successful reception and the most reliable estimation of the loud packet. However, this is not mandatory. Packets other than loud packets may be transmitted at low power for trade-off to other system variables.

In order for the receiving WTRU to know which WTRU the path loss estimate corresponds to, the identifier (eg, MAC address) of the WTRU transmitting the loud packet must also be included in the information field.

In addition, the loud packet may be implemented by any current signal frame selected by the transmitter and transmitted with a known transmit power by the receiver. For example, the transmit power may be explicitly known by the receiver from an information element (IE) added or piggybacked in the current signal frame. In addition, the transmit power of the loud packet may be known by the receiver as part of the preferred signal exchange with the sender of the loud packet.

In one advantageous implementation, a beacon / probe response frame is used to serve as a loud packet. Each transmit power may be part of the beacon / probe request frame itself, or the agreed predetermined transmit power setting of these frames is communicated to the WTRU by other means, such as adjacent information signals.

Loud  Additional information reported in the packet

The loud packet can be used as a flexible reporting mechanism to help the receiving WTRU optimize its parameters (transmit power, EDT, DT). The following variables may be reported by the transmitting WTRU (transmitter) (in addition to the WTRU identifier and transmit power of the loud packet or as an independent signal, if necessary).

1) In an infrastructure BSS, an identifier (and / or BSS, IBSS, or mesh identifier) or address of an AP associated with a WTRU.

2) Power used to transmit packets other than loud packets.

3) Estimated list of path losses to other WTRUs recognized by the transmitter.

4) A list of signal strengths (or their average) of packets received by the transmitter from other WTRUs (one value for each other WTRU).

5) The complete period list of packets received by the transmitter from other WTRUs within a specific time (one value for each other WTRU).

6) EDT known by or used by the transmitter for another WTRU.

7) Clear Channel Assessment (CCA) mode known by the transmitter or used by the transmitter for other WTRUs.

8) A DT known to the transmitter for another WTRU or used by the transmitter to transmit a packet.

Piggyback  option

To limit the amount of signal bandwidth used, loud packets may be piggybacked into other types of packets (including traffic, control, or management information). In this case, the entire packet should preferably be sent at the power of the loud packet.

Loud  Coordination Management of Packet Transmission

The transmission of the loud packet need not be limited to a specific WTRU. However, this transmission is preferably controlled to some extent by the coordinating node. Typically, the AP should act as a coordinating node in the infrastructure BSS. The generation of loud packets by the coordinating node has the advantage of ensuring minimal performance depending on the localization technique or the specific delay management technique used in the system.

1 is a signal flow diagram which is transmitted to a wireless communication system 100 is loud packets within a coordinating node from the at least one _{(105) WTRU (110 1 -110} N) constructed in accordance with the subject innovation. Management of loud packet transmission may be accomplished by signaling from the coordinating node 105 (eg, AP) to one or more WTRUs 110 to send the loud packet. Such signaling may be executed by the coordination node 105 which first sends the loud packet transmission request message 115 to the WTRU 110. The loud packet generation request message 115 may be a broadcast message, multicast message, or unicast message to all WTRUs 110 (eg, all WTRUs of a BSS) under the control of the coordinating node 105. The loud packet generation request message 115 may be added to one of the current IEEE 802 signal exchanges, such as, for example, a frame contained within an association / authentication or admission control procedure.

The information included in the loud packet generation request message 115 may indicate one or more of the following:

1) The transmit power to use for the loud packet.

2) Information to report in the loud packet (among all the possible fields described above).

3) Timing of transmission of one or more loud packets. Several options are possible, including but not limited to:

i) Periodically or quasi-periodically in a specific period between successive transmissions of loud packets.

ii) a specific number of times within a particular time window (eg, once)

iii) after a certain condition (trigger) is satisfied, such as a) packet detection sent by a new WTRU, or b) the number of packets retransmitted within a certain time period above a certain threshold.

4) Number of received packets that are packets that are retransmitted within a certain time period above a certain threshold.

5) Indication whether the loud packet should be piggybacked on another packet or not.

6) Information about loud packet generation by other WTRUs (ie all of the above for WTRUs other than the receiving WTRU).

The WTRU receiving the loud packet generation request message 115 selectively responds to the loud packet generation response message 120, as shown in FIG. 1. The loud packet generation response message will indicate the transmit power that the WTRU will use to send the loud packet (if not specified in the request message or otherwise different from the requested). This is useful if the transmit power of the loud packet is not indicated within the loud packet itself. In one embodiment, the loud packet generation request will be included in the field of the loud packet. Thus, the loud packet generation request message itself will be used by one WTRU to estimate the path loss to another WTRU.

Loud  Non-Coordination Management of Packet Transmission

As an alternative to the coordination management approach as described above, the WTRU may automatically determine when to send a loud packet and what information to report to them. This behavior may be agreed in advance to WTRUs that follow certain standards.

Another approach is to allow any WTRU (as well as the coordinating node) to send a loud packet generation request message to another WTRU. Such techniques would be suitable in ad-hoc and mesh systems.

Support for Smart Antenna

The above description is suitable for WTRUs using simple antennas. In order to support a WTRU equipped with a smart antenna (ie multi-beam or switched-beam antenna), it may be useful to include some additional information in the loud packet:

1) The antenna beam used by the WTRU to send the loud packet (can be specified in the loud packet generation request message by the coordinating node). The path loss between the first WTRU and the second WTRU depends on which antenna beam is used. If the WTRU transmitting the loud packet can use different antenna beams, the receiving WTRU will know that one of these beams has been used to transmit the loud packet, so that the path loss measurement should be related to which antenna beam. .

2) Antenna beam used by the WTRU to transmit packets other than loud packets. Advanced delay management algorithms need to know this information in order to properly set the variable (eg, delay threshold) of the receiving WTRU.

3) Antenna beam used by the WTRU to receive packets. This is the antenna beam used for reception by the WTRU transmitting the loud packet rather than the WTRU receiving the loud packet. Thus, a WTRU sending a loud packet notifies other WTRUs each time it receives a packet and uses a specific antenna beam that may be different than what is currently used to send the loud packet. This information is useful for other WTRUs, so that other WTRUs know whether a transmission at a particular power will result in a delay (or non-delay) at this WTRU.

2 is a block diagram of a wireless communication system including a plurality of WTRUs 205 ₁ , 205 ₂ , each using smart antennas 222, 224 to transmit and receive loud packets according to the present invention. The WTRU 205 ₁ includes a processor 210, a transmitter 215, and a receiver 220. WTRU 205 ₂ includes a processor 225, a transmitter 230, and a receiver 235.

Processors 210 and 225 of the WTRU 205 may each transmit a loud packet, a loud packet generation request message 115 and, optionally, transmitters 215 and 230 and smart antennas 222 and 242 respectively. And generate a packet generation response message 120. In addition, each receiver 220, 235 of the WTRU 205 may have a loud packet to be processed by the processor 210, 225, a loud packet generation request message 115, and, optionally, a loud packet generation response message 120. Is configured to receive a.

Using the loud packet information, the WTRU 205 receiving the loud packet may determine a robust path loss estimate for each antenna beam of the smart antennas 222 and 242 used by the WTRU 205 to transmit and receive the loud packet. have. It is to be understood that "path loss" includes the gain due to the transmit / receive antenna, and that other beams are used to transmit and receive different loudspeakers.

3 is a flow diagram of a process 300 for estimating path loss between two WTRUs in accordance with an embodiment of the present invention. Process 300 is executed in a wireless communication system such as system 200 of FIG. 2 including a plurality of WTRUs 205 ₁ and 205 ₂ . The first WTRU 205 ₁ transmits a loud packet (step 305). The second WTRU (205 ₂₎ receives a loud packet and determines (step 310), determining a signal strength (dB) of the received loud packets (step 315), the transmission power of received loud packets (dB) ( For example, by obtaining transmit power from the loud packet itself or from the loud packet generation request message indicating which transmit power should be used (step 320). The WTRU 205 ₂ subtracts the signal strength determined in step 315 from the transmit power determined in step 320 to determine the path loss between the WTRU 205 ₁ and the WTRU 205 ₂ (step 325).

4 is a flow diagram of a process 400 of estimating a path loss between two WTRUs based on information included in a loud packet generation request message sent by a coordination node according to another embodiment of the present invention. The process 400 adjusts the node 105 and the plurality of the WTRU (110 ₁ - 110 _N) are executed in a wireless communication system, such as system 100 of Figure 1 comprising a. The coordination node 105 sends a loud packet generation request message (step 405). The first WTRU 110 receives a loud packet generation request message (step 410). In optional step 415, the first WTRU responds to the loud packet generation request message by sending a loud packet generation response message. At step 420, the first WTRU transmits at least one loud packet including the information specified by the loud packet generation request message. In step 425, the second WTRU 110 receives at least one loud packet, determines the signal strength (dB) of the received loud packet (step 430), and receives the received loudness based on the information contained in the loud packet. The transmit power (dB) of the packet is determined (step 435). In step 440, the second WTRU determines the path loss between the first WTRU and the second WTRU by subtracting the signal strength determined in step 430 from the transmit power determined in step 435.

5 is a flow diagram of a process 500 for estimating a path loss between two WTRUs based on a condition specified by a loud packet generation request message sent by a third WTRU in accordance with another embodiment of the present invention. The first WTRU of the plurality of WTRUs sends a loud packet generation request message (step 505). The second WTRU of the plurality of WTRUs receives a loud packet generation request message (step 510). In optional step 515, the second WTRU responds to the loud packet generation request message by sending a loud packet generation response message. In step 520, the second WTRU transmits at least one loud packet based on a condition specified by the loud packet generation request message (e.g., transmits at a specific transmit power, at a specific time using a particular antenna beam, such as a smart antenna). do). In step 525, the third WTRU receives at least one loud packet, determines the signal strength (dB) of the received loud packet (step 530), and determines the transmit power (dB) of the received loud packet (step 535). In step 540, the third WTRU determines the path loss between the second WTRU and the third WTRU by subtracting the signal strength determined in step 530 from the transmit power determined in step 535.

In conventional wireless communication systems, path loss estimation for neighboring WTRUs is quite uncertain due to the lack of knowledge of the transmit power of neighboring WTRUs. The only signaling that allows the WTRU to know at what power the packet was sent is a TCP request / report that requests dedicated bidirectional signaling and cannot be established periodically. This issue is emphasized in the present invention by having the transmit power of the WTRU directed in the loud packet itself or otherwise.

In addition, in a conventional wireless communication system, a WTRU transmitting at a power much lower than the maximum transmission level could not be heard by other WTRUs in a large area, which prevents any path loss estimation performed. In scenarios where the WTRU aims for delay variable adjustment, it may be desirable to estimate the path loss at which the WTRU separates itself from other neighboring WTRUs, even if the WTRU cannot recognize neighboring WTRUs at the current transmit power. will be. The present invention solves this problem.

In addition, in a conventional wireless communication system, the WTRU did not accurately estimate the path loss that separates it from neighboring WTRUs if the WTRUs are not related to the same BSS. The present invention provides a solution to this problem by controlling the generation of loud packets by the WTRUs.

Finally, there is no support for path loss estimation in conventional wireless communication systems with WTRUs equipped with smart antennas. The present invention supports the inter-WTRU path loss estimation when the WTRU is equipped with a smart antenna.

While features and elements of the present invention have been described as preferred embodiments in particular combinations, each feature and element may be used alone (without other features and elements of the preferred embodiments), or with or without features and elements of the present invention. It can be used in various combinations.

Claims (18)

A wireless transmit / receive unit (WTRU) for estimating path loss, wherein the WTRU is: A receiver receiving the loud packet, A processor electrically coupled to the receiver, The processor is configured to determine a signal strength of the received loud packet, a transmit power of the received loud packet, and a path loss between a first WTRU and a second WTRU; And the path loss is calculated by subtracting the determined signal strength from the determined transmit power. 2. The system of claim 1, further comprising a transmitter electrically coupled to the processor, And the transmitter is configured to transmit a loud packet generation request message. 2. The system of claim 1, further comprising a transmitter electrically coupled to the processor, And the transmitter is configured to transmit a loud packet generation response message in response to the receiver receiving the loud packet generation request message. A smart antenna configured to generate a plurality of antenna beams for transmitting and receiving loud packets; A receiver, electrically coupled to the smart antenna, configured to receive a loud packet generation request message; A processor electrically coupled to the receiver and configured to generate at least one loud packet based on information in the loud packet generation request message; The at least one loudspeaker, electrically coupled to the processor and the smart antenna, using an antenna beam generated by the smart antenna in accordance with information obtained in a loudspeak packet previously received through the smart antenna and the receiver. A wireless transmit / receive unit (WTRU) comprising a transmitter configured to transmit a signal. A smart antenna configured to generate a plurality of antenna beams for transmitting and receiving loud packets; A transmitter electrically coupled to the smart antenna, the transmitter configured to transmit a loud packet generation request message; A receiver electrically coupled to the smart antenna, the receiver configured to receive a plurality of loud packets; And a processor electrically coupled to the transmitter and the receiver and configured to determine path loss associated with different antenna beams used to receive the loud packet. An integrated circuit (IC) embedded within a wireless transmit / receive unit (WTRU) for estimating path loss, A receiver configured to receive a loud packet, A processor electrically coupled to the receiver, the processor configured to determine a signal strength of the received loud packet, a transmit power of the received loud packet, and a path loss between a first WTRU and a second WTRU; And wherein said path loss is calculated by subtracting said determined signal strength from said determined transmit power (IC) embedded within a wireless transmit / receive unit (WTRU). 7. The integrated circuit of claim 6, further comprising a transmitter electrically coupled to the processor, the transmitter further configured to transmit a loud packet generation request message. 7. The integrated circuit of claim 6, further comprising a transmitter electrically coupled to the processor, the transmitter further configured to transmit a loud packet generation response message in response to the receiver receiving a loud packet generation request message. An integrated circuit (IC) embedded within a wireless transmit / receive unit (WTRU) having a smart antenna configured to generate a plurality of antenna beams for transmitting and receiving loud packets. A receiver configured to receive a loud packet generation request message; A processor electrically coupled to the receiver and configured to generate at least one loud packet based on information in the loud packet generation request message; And electrically coupled to the processor and configured to transmit the at least one loud packet using an antenna beam generated by the smart antenna in accordance with information obtained within a loud packet previously received via the smart antenna and receiver. An integrated circuit embedded in a wireless transmit / receive unit (WTRU) comprising a transmitter. An integrated circuit (IC) embedded within a wireless transmit / receive unit (WTRU) having a smart antenna configured to generate a plurality of antenna beams for transmitting and receiving loud packets. A transmitter electrically connected to the smart antenna, the transmitter configured to transmit a loud packet generation request message; A receiver electrically connected to the smart antenna and configured to receive a plurality of loud packets; An integrated circuit (IC) embedded in a wireless transmit / receive unit (WTRU) electrically coupled to the transmitter and receiver, the processor comprising a processor configured to determine path loss associated with different antenna beams used to receive the loud packet. . A device for coordinating the management of loudspeakers used to estimate path loss, A coordination node comprising a first processor for generating a loud packet generation request message, and a first transmitter coupled to the first processor and configured to transmit the loud packet generation request message; A plurality of wireless transmit / receive units (WTRUs) in communication with the coordination node over a wireless medium, The first WTRU of the WTRU is, A first receiver configured to receive the loud packet generation request message; A second transmitter configured to transmit at least one loud packet; A second processor electrically coupled to the receiver and the transmitter and controlling the second transmitter to transmit the at least one loud packet at a transmit power specified by the loud packet generation request message; The second WTRU of the WTRU is, A second receiver configured to receive the at least one loud packet; The path loss between the first WTRU and the second WTRU is determined by determining the signal strength of the received loud packet, determining the transmit power of the received loud packet, and subtracting the determined signal strength from the determined transmit power. And a third processor configured to determine. 12. The apparatus of claim 11 wherein the coordination node is an access point (AP). 12. The apparatus of claim 11, wherein the second transmitter is configured to send a loud packet generation response message when the first receiver receives the loud packet generation request message. 14. The apparatus of claim 13, wherein the loud packet generation response message indicates the transmit power that the first WTRU will use to transmit the loud packet. A device for coordinating the management of loudspeakers used to estimate path loss, A coordination node comprising a first processor for generating a loud packet generation request message, and a first transmitter coupled to the first processor and configured to transmit the loud packet generation request message; A plurality of wireless transmit / receive units (WTRUs) in communication with the coordination node over a wireless medium, The first WTRU of the WTRU is, A first receiver configured to receive the loud packet generation request message; A second transmitter configured to transmit at least one loud packet at a time specified by the loud packet generation request message; A second processor electrically coupled to the receiver and transmitter and controlling the second transmitter to transmit the at least one loud packet at a transmit power specified by the loud packet generation request message; The second WTRU of the WTRU is, A second receiver configured to receive the at least one loud packet; The path loss between the first WTRU and the second WTRU is determined by determining the signal strength of the received loud packet, determining the transmit power of the received loud packet, and subtracting the determined signal strength from the determined transmit power. And a third processor configured to determine. 16. The apparatus of claim 15, wherein the coordination node is an access point (AP). 16. The apparatus of claim 15, wherein the first WTRU responds to the loud packet generation request message by sending a loud packet generation response message. 16. The apparatus of claim 15, wherein the loud packet generation response message indicates the transmit power that the WTRU will use to transmit the loud packet.

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