MXPA06006977A - Unscheduled power save delivery method in a wireless local area network for real time communication - Google Patents

Abstract

A mobile station (106) establishes a real time communication link via an access point (102) for carrying voice or other time-sensitive data. A WLAN subsystem (204) of the mobile station is normally kept in a low power state. Upon initiating a communication link the mobile station signals to the access point that unscheduled power save delivery mode will be used (614), and the access point reserves resources to assure the necessary quality of service. The mobile station initiates a frame transaction by first powering up the WLAN subsystem (712), acquiring the WLAN channel (407), and transmitting a polling frame. Upon successful receipt of the polling frame the access point prepares to reply with an aggregate response. The aggregate response commences by transmitting all data in an aggregate buffer, including both reserved and unreserved data buffers. Upon successful receipt of the aggregate response, the mobile station places the WLAN subsystem back into a low power state.

Description

SE, SI, SK, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, For two-letter codes and other abbreviations, refer to the "Guid-GQ, GW, ML, MR, NE, SN, TD, TG.) Anee Notes on Codes and Abbreviations "appearing at the begin- _,,. ,, nine ofeach regular issue of the PCT Gazette. Published: ó J 6 J "METHOD OF NON-SCHEDULED SUPPLY OF SAVINGS OF ENERGY IN A WIRELESS NETWORK OF LOCAL AREA FOR THE REAL-TIME COMMUNICATION " FIELD OF THE INVENTION This invention relates generally to wireless local area networks, and more particularly to energy saving methods for reducing the power consumption in a mobile station while connecting to a time sensitive communication activity.

BACKGROUND OF THE INVENTION Wireless LAN (WLAN) systems that provide broadband wireless access have experienced a dramatic increase in popularity in recent years. Although the main application of these systems has been to provide network connectivity to portable and mobile devices that run data applications such as, for example, email and web browsing, there has been a growing and tremendous interest in supporting such isochronous services. as a telephony service and real-time video broadcast. One of the key issues facing the designers of wireless systems when they consider voice services and other time-sensitive services in a WLAN connection, such as that described by the IEEE 802.11 specification, is the power consumption of portable devices. For example, in order to deliver a talk time and competitive waiting time, compared to wireless or cellular digital devices, energy conservation becomes necessary during voice calls. Several organizations have proposed an energy efficient operation by transmitting power control and adapting physical layer rate for systems that are based on a centrally controlled non-containment channel access scheme. However, such approaches can be complex to implement and may not provide the energy savings required to justify the complexity.

BRIEF DESCRIPTION OF THE INVENTION The 802.11 standard defines the procedures that can be used to implement energy management in a portable device during periods of inactivity. In particular, three different building blocks are provided to support the energy savings: an Awakening Procedure, a Sleeping Procedure, and an Energy Saving Consultation Procedure (PS-Power-save Poly query). A mobile client voice station (mobile station) can combine these building blocks in various ways to support power management for different applications. Awakening Procedure: There are generally two reasons for the mobile station to wake up, namely to transmit pending data or recover data placed in the temporary memory from the fixed station that provides service to the mobile station, known as the access point. Awakening to transmit data is a direct operation, triggered by the mobile station. The decision to wake up and receive data is also made by the mobile station after monitoring its pending data bit in a periodic beacon frame transmitted by its access point. Once the mobile station decides to transition from sleep mode to active mode, it notifies the access point by sending an uplink link frame with the energy saving bit (PS - power-save) set to active. After such transmission, the mobile station remains strip so that the access point can send with Subsequent any downlink frames placed in temporary memory. Sleeping Procedure: Similar to the awakening procedure, a mobile station in the active mode needs to complete a successful frame exchange sequence initiated by the mobile station with the PS bit set to sleep to make the transition to sleep mode. After this frame exchange sequence, the access point places all the downlink frames to this mobile station in temporary memory. PS Query Procedure: Instead of waiting for the access point to transmit the downlink frames placed in temporary memory, a mobile energy-saving station can request an immediate supply from its access point using a Query frame. of PS. After receiving this PS Query, the access point can immediately send a downlink frame placed temporary memory (immediate data response) or simply send a recognition and response message with a data frame afterwards (delayed data response) ). In the case of an immediate data response, a mobile station may remain in the sleep state after _? _ to terminate this exchange of frames since there is no need for the mobile station that chooses the transition to the active state since the access point can only send a downlink frame placed in temporary memory after receiving a PS Query from the mobile station. On the other hand, in the case of a delayed data response, the mobile station has to make the transition to the active state until receiving a downlink frame from the access point. The architecture of a simple enterprise WLAN system is graphically represented in Figure 1. Referring now to Figure 1, a summary 100 of the system block diagram of a typical enterprise WLAN system is shown. It includes an infrastructure access network 101, consisting of an Access Point 102 and mobile stations such as a data station 104 and a voice station 106. The mobile stations are connected to the access point by a radio link 108 of WLAN The access point is wired to some distribution network, including the voice and data network accesses 110, 112 respectively, by means of a switch 114. The voice station executes a Voice over IP (VoIP) application. ), which establishes a connection point-to-point with the voice network access, which represent the other end of the voice call, and which routes the voice data to a voice network 116. The data stations can be connected to the data network access by means of the access network and can be connected, for example, to a wide area network 118. The impact of data traffic on voice quality should be considered. It is assumed that both voice and data stations employ a quality of service mechanism based on hierarchical containment. The VoIP traffic characteristics make WLAN voice applications exceptionally suitable for an energy saving operation. In particular, VoIP applications periodically generate speech frames, where the inter-arrival time between the frames depends on the voice encoder selected for an application. The process for encapsulating voice frames in IP packets is commonly referred to as packetization, which is often assumed to occur once every 20 milliseconds. A typical VoIP conversation involves a bidirectional constant bit rate flow of VoIP frames, which includes an uplink flow from the handset to a voice network access and a downlink flow in reverse direction. Since the station generally knows in advance the arrival rate of the frame, the delay, and the bandwidth requirements of its voice application, it can reserve resources and configure power management for its voice flows in accordance with the access point. A mobile station can be deprived of the power saving mode, and remain in active mode, always ready for the downlink voice transmission. In this case, the access point can transmit downlink voice frames as they arrive. However, you want to save energy, the mobile station can use the energy-saving building blocks described above to wake up, exchange the VoIP frame with your access point, and go back to sleep. In a shared intermediate network, such as the access network shown in Figure 1, it is important to rank VoIP traffic over traffic that requires only the best effort delivery, such as traffic generated by application that can be adapted to the amount of bandwidth available in the network and does not request or require a minimum performance of process and transfer or delay. The hierarchy allows the system to minimize the delay experienced by traffic sensitive to delays. A containment-based channel access scheme that offers hierarchical access called Enhanced Distributed Channel Access (EDCA) has been specified in the IEEE 802 draft., and is suitable for VoIP applications. It is based on the Multiple Access Carrier Detection with Collision Evasion (CSMA / CA - Carrier Multiple Sensing Access with Colusion Avoidance) mechanism defined in 802.11. The stations with voice frames to send first must detect the activity of the channel, before transmitting. If the channel has been inactive for at least a specified period of time, called the arbitration interframe space (AIFS), the mobile station can immediately begin its transmission. Otherwise, the mobile station disconnects and waits for the channel to be inactive for a random amount of time, which is equal to a period of AIFS plus a value evenly distributed between zero and a window time period value of containment (CW contention window). The CW is limited in addition to the Minimum containment window (CWmin) and the Maximum containment entry (CWmax). The EDCA provides hierarchical access control by adjusting the containment parameters: AIFS, CWmin, and CWmax. By selecting different values of AIFS, CWmin, and CWmax for different access categories, the priority for accessing the medium can be regulated and differentiated. In general, small values of AIFS, CWmin, and CWmax result in a higher access priority. It is possible for a mobile station to use information such as the inter-arrival time of the downlink voice frames, together with an energy saving mechanism, to put itself to sleep between two frames of two consecutive frames. Currently there are energy saving procedures described in various documents and specifications related to the WLAN. The first power management mechanism of the prior art uses a bit in the packet header. The bit is designed as a power management bit (PM-power management) to indicate the change in the energy status of the mobile station to the access point. First, a mobile station makes the transition from sleep mode to active mode after having an uplink data frame that transmits setting the PS bit in active in an uplink voice frame in order to notify the change of its energy state. Knowing that there will be a corresponding downlink frame placed in the temporary memory at the access point, because the uplink and downlink vocoders share the same voice frame duration, the mobile station remains in active mode for the downlink transmission. After receiving the uplink transmission, the access point then sends temporary memory downlink frames to the mobile station. In the last downlink frame, the access point sets the "more data" type to FALSE in order to communicate the end of the downlink transmission. Finally, the mobile station needs to complete a successful sequence of exchange of frames initiated at the station with the PS bit set to sleep to make the transition to sleep mode. (for example, an uplink frame, a null frame if there is no uplink data frame to be transmitted, with the PS bit set to sleep). In the following context, the mechanism based on the PS bit is referred to as LGCY6 in the matter.

A second power management mechanism uses a PS Query frame to request the downlink frames. Instead of waiting indefinitely for the access point to deliver the downlink transmission, the mechanism based on the PS Query uses the PS Query frame to retrieve the downlink frame placed in the access memory's temporary memory. First, a mobile station makes the transition to active mode after having to transmit an uplink data frame. The mobile station then sends the uplink transmission. Similar to the mechanism based on the PS bit, the access point sets the field plus data to indicate the presence of some downlink transmission placed in temporary memory. If the bit plus da cough is TRUE, the mobile station will continue to send a PS Query frame in order to recover the downlink frame placed in temporary memory. Unlike the mechanism based on the PS bit, a mobile station can remain in the sleep state since the access point responds to the PS Query with an immediate data frame. At . In the following context, the mechanism based on the PS Consultation is referred to as LGCY5 in the matter.

There are a couple of issues to support the efficient energy VoIP operation using the current WLAN power saving mechanisms. First, the mechanism based on the PS bit is somewhat inefficient because, for example, the 802.11 standard currently offers only one way for the mobile station to transition to sleep mode, which initiates a frame exchange sequence with the PS bit set to sleep. As a result, an exchange of extra frames initiated in a mobile station by bidirectional voice transfer is needed in order for the mobile station to signal the transition of the energy state. Since the payload of a speech frame is small (for example, 20 bytes for voice application with a 20 ms framework and an 8 Kbps vocoder), the additional information incurred by the exchange of extra frames could be so high as a third party of the traffic between the mobile station and the access point. Significant supplementary information results in inefficiency of both energy consumption and system capacity. A second issue is related to the quality of the service. Under the mechanism based on PS Query, since a mobile station is not aware of the Priority of the downlink frame placed in temporary memory, the PS Query frame is sent as a best effort access attempt, which is a data traffic mode instead of a voice traffic mode. As a result, downlink voice transmissions essentially use the best effort priority instead of the highest voice priority. When a system is loaded with both data traffic using the best effort priority with voice traffic, such as a mobile station that retrieves the downlink voice traffic using an energy saving query frame transmitted at the same priority as Data traffic, the system will be unable to protect voice traffic from the delays associated with a better congested effort supply system. The legacy power saving methods may also require an uplink or query frame to retrieve each frame placed in temporary memory for the downlink, or require immediate response from the access point for a particular uplink frame. One method for providing a particular quality of service is to use scheduled service periods at regular intervals for a given mobile station. This programmed mode of Energy saving supply is referred to as automatic energy saving supply (APSD - Automatic Power Save Delivery). The mobile station wakes up at regular intervals and listens to the channel. The access point is synchronized with the service period, and transmits data in the programmed time. Consequently, the mobile station can place the WLAN subsystem to sleep during the periods between the scheduled service intervals. However, this method limits the flexibility of the WLAN channel since there is no ability for the mobile station to deviate from the program. Therefore, given these drawbacks of the prior art, there is a need for a reliable power management protocol in a WLAN system that allows the mobile station with active voice sessions to efficiently enter and exit the energy saving mode without excessive supplementary information and maintaining the quality of service in the presence of a lower priority traffic.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a summary of the block diagram of a typical enterprise WLAN system which can support both prior art methods of WLAN transactions as well as those according to the present invention. Figure 2 shows a schematic block diagram of a mobile station for use in a WLAN system, according to the invention; Figure 3 shows a schematic block diagram of an access point for use in a WLAN system, according to the invention; Figure 4 shows a flow diagram illustrating a summary of the traffic flow between a mobile station and an access point in a system of WLAN to support speech quality communication, in accordance with the invention; Figure 5 shows a service interval and query synchronizer diagram for use with the invention; Figure 6 shows a state transition diagram illustrating how a mobile station informs an access point about the energy saving mode that is used by the mobile station, according to the invention; Figure 7 shows a flow chart illustrating a method used by a mobile station to utilize the unscheduled power saving mode of supply, according to the invention; Figure 8 shows a flow chart of a mobile station frame exchange process, according to the invention; Figure 9 shows a flow diagram of a method for temporarily storing data at an access point, according to the invention; and Figure 10 shows a flowchart of a method for removing from the temporary memory data at the access point for use in an unscheduled energy saving mode of supply, according to the invention.

DETAILED DECRIPTION OF THE INVENTION Although the specification concludes with the claims that define the features of the invention that are considered as novel, it is considered that the invention will be better understood from a consideration of the following description in conjunction with the drawings, in which: which are reported similar reference numbers. The invention solves the problems associated with the prior art by providing an unscheduled power save delivery (UPSD) mode of operation in a wireless local area network (WLAN) system. which allows a mobile station in energy saving mode to recover the frames from an access point without requiring the access point to respond immediately to a query frame, without requiring the mobile station to query the access point for each frame of downlink, and without requiring the mobile station to transmit a frame to inform the access point about a transition to a low power mode. In addition, it allows the mobile station to receive an aggregate supply of data, which includes both data for reserved streams as well as "Best Effort" data, or non-reserved data.When the mobile station uses the present energy saving mode of UPSD first establishes a resource reservation with an access point that indicates its intention to use the UPSD mode to recover data from the access point during the operation of the energy savings. use the UPSD mode for the information in the traffic specification admission control frame sent to the access point from the mobile station During the call configuration negotiation, the access point reserves sufficient resources to ensure a session of voice quality, and identifies the. flow with a unique traffic flow identifier which is subsequently used by the mobile station to activate a state transition to the unscheduled energy saving mode of delivery. Alternatively, the mobile station and the access point can negotiate a reservation of resources for a full access category, which represents an aggregate traffic flow comprised of one or more individual traffic flows. The access category is defined as the traffic priority associated with the reserved flow compared to other reserved flow access categories. The priority is determined in part by the minimum waiting period to be used in the containment of the access category. If the admission control module makes a decision based on traffic flows or access categories, it is said that reserving resources is to support the flow of traffic, and all data associated with the flow of reserved traffic is identified as such. . Once the intention to use the present energy saving mode is communicated to the access point, the mobile station begins to place the WLAN subsystem circuitry into a low power mode, such as turning off the chipset from the WLAN and associated circuits. In In the preferred embodiment, the mobile station operates the WLAN subsystem according to a time period of service intervals while connecting to a WLAN voice session. The service interval is defined as the real-time duration of the data contained in a data frame. Typically, for example, the service interval for voice traffic is in the order of 20 milliseconds. However, in practice, the current time between the service periods varies slightly from the defined service interval due to factors such as the inter-arrival time between the frames and other small fluctuating delays inherent in large networks. The mobile station initiates a period of frame exchange service with the access point upon waking the WLAN subsystem. That is to say, the WLAN subsystem makes the transition from the low power mode to the fully active mode, referring here to the current state of the energy level of the WLAN subsystem, and not the state of the energy saving signaling bits in the frames sent to the access point . If the voice processor of the mobile station has produced a data packet to be transmitted, the WLAN subsystem begins to acquire the WLAN channel to transmit the data to the point with a query frame, identify the query frame as belonging to the reserved traffic flow, or identify it as one of the reserved traffic flows if more than one has been admitted for the mobile station by the access point. If there is no data available, the WLAN subsystem waits preferably until the expiration of a query window synchronizer, at which time if no data has yet to be sent by the voice processor, the WLAN subsystem acquires the WLAN channel and transmits a null frame as the query frame. In the query frame, according to an alternative embodiment of the invention, the mobile station can direct the access point to transmit an aggregate response, implying that the access point will transmit not only data for the reserved traffic flow, but any other data that the access point could also have placed in temporary memory for the mobile station. In the preferred mode, the access point will transmit an acknowledgment in response to receiving the query frame. After that, the access point transmits an aggregate response frame to the mobile station. If the access point has data placed in temporary memory in a temporary memory reserved for the reserved traffic flow, the response frame will include that data. If the access point has other data, such as non-reserved flows, the access point may also transmit the data with the reserved flow data. If the access point has no reserved data or has non-reserved data, a null frame is transmitted to the mobile station, or alternatively the access point recognition of the query frame may indicate that there is no data in the temporary memory added of the access point for the mobile station. If the access point has more than one data frame, then the access point indicates this in the header information of the response frame. Alternatively, the access point may send data of any type that has been placed in the temporary memory for the mobile station, regardless of the state of data admission. The mobile station that maintains the WLAN subsystem in active mode until the data placed in temporary memory from the access point is received. In the preferred mode, the mobile station recognizes each response frame when transmitting an acknowledgment. Once all the data placed in temporary memory from the access point for the present service period are received, the mobile station places the WLAN subsystem back into the low power mode. Referring now to Figure 2, a schematic block diagram 200 of a mobile station is shown for use in a WLAN system, according to the invention. The mobile station comprises a voice processor 202 for processing speech signals, which includes transforming signals between the analog and digital form. The speech processor is operatively coupled to a WLAN subsystem 204. The voice subsystem contains temporary data memories and radio hardware for sending and receiving information about a wireless radio frequency link via an antenna 206. The voice processor converts the digital voice and audio data received from the WLAN subsystem into analog form and reproduces them by a transducer, such as a speaker 208. The speech processor also receives analog voice and audio signals from a microphone 210, and converts them into digital signals, which are sent to the WLAN subsystem. Preferably, the speech processor also performs speech encoding and coding, using, for example, predictable linear coding techniques excited by vector addition, as is known in the art. The use of voice coding allows the compression of voice data. In addition to voice processing, the mobile station may have other media processors, summarized as box 212, which may include regular data applications such as e-mail, for example. These other data processors are operatively coupled in a manner similar to the WLAN subsystem via bus 214, for example. As the data arrives in the WLAN subsystem, it is placed in temporary memory in the temporary memory 216 of the WLAN and subsequently packaged for transport over the IP networks. Each processor that sends data to the WLAN subsystem indicates the type of data, and formats the data for transmission, indicating the type of data in the frame. All data processors and the WLAN subsystem are controlled by a controller 218. The controller dictates the power saving operation of the WLAN subsystem, setting it to lower power states when appropriate and turning it on when it is time to transmit or to receive data. Referring now to Figure 3, there is shown a schematic block diagram 300 of an access point for use in a WLAN subsystem, according to the invention. A WLAN transceiver 302 executes the necessary radio frequency operations for communicating with the mobile stations in the vicinity of the access point via an antenna 304. The access point is connected to the networks via the access network interface 306, typically by a hard line 316, such as a coaxial cable, for example . The data received at the access point from the mobile stations is immediately sent in advance to the network access to be routed to the appropriate network entity. The data received at the access point from the network that is connected to a mobile station can be treated according to one of at least three classifications. First, the mobile station may be in active mode, in which case the data will only be placed in temporary memory until they can be transmitted. In such a case, the intention is not to delay transmission to the mobile station any longer than necessary, and the data for a mobile station of this classification is typically transmitted using a query discipline based on priority. A second category of energy saving state of the mobile station is a mobile station in a non-reserved or legacy energy saving mode. For this second classification, a temporary memory administrator 308 places the data in a memory in temporary memory 310 of non-reserved data after receiving them from network access 306 via a bus 318. Non-reserved data is data that does not belong to a reserved traffic flow. When the particular mobile station for which the non-reserved data is placed in temporary memory transmits to the access point either an energy saving query frame of non-reserved data or a frame performing the transition from the mobile station to the active state, the access point will respond by transmitting the non-reserved data to the querying station from the temporary memory of non-reserved data. The mode of delivery can be controlled by the mobile station, where the non-reserved data is sent only in response to a specific inquiry or activation frame, or it can be sent at scheduled and regularly scheduled time intervals. A third energy saving classification of the access point can receive data for its reserved data bound for a mobile station using the present energy saving mode of UPSD, according to the invention. The reserved data is data belonging to a reserved traffic flow. For this reserved flow data, the temporary memory administrator 308 places the data in a memory in the temporary memory UPSD temporary, such as reserved temporary memory 312. Reserved temporary memory means that the temporary memory is to place in temporary memory data pertaining to a reserved traffic flow. Although illustrated here as two separate physical time memories, one skilled in the art will understand that a variety of temporary memory placement techniques can be used to keep reserved and non-reserved data separate, without necessarily requiring separate physical time memories. In addition, since the access point will respond to the query frame with an aggregate response, the temporary memory of non-reserved data and the temporary memory of UPSD can be treated as an aggregate temporary memory 309. The intention of the invention is that when the The access point is consulted by the mobile station, it empties the added temporary memory by transmitting all the data placed in the temporary memory added to the mobile station. Since the data associated with the reserved traffic flow is time sensitive, the access point preferably maintains a seniority classification policy. In the preferred embodiment of the invention, the classification policy by age it only allows two data frames to be placed in temporary memory for a reserved traffic flow. If there are two frames currently in temporary memory, and a third frame arrives, then the oldest frame is discarded, and the new frame is placed in temporary memory. Supervising the operation of the temporary memory manager 308, the network access 306, and the transceiver 302 is a controller 314. The controller also manages the resource management and controls the resources so that the quality of service can be ensured as necessary for reserved traffic flows. The controller is operatively coupled to a memory 315, which is used to track the state of the call, the energy saving states of the mobile station, and other parameters. Referring now to Figure 4, there is shown a flow chart 400 illustrating a summary of the traffic flow between a mobile station and an access point in a WLAN system to support voice quality communication using the present mode of UPSD of the invention. The traffic flow includes a reserved traffic flow, which means that the mobile station and the access point have negotiated a priority and the average time for the reserved traffic flow to ensure a desired communication quality, where the average time indicates the amount of time per negotiated service interval that the access point will distribute to the traffic flow or access category. With voice traffic, since it occurs in real time, it is desirable to establish a traffic flow reserved for communication. The system executing the flow shown here in Figure 4 can be executed by a system using configurations and system components similar to those shown in Figures 1-3 with control software designed in accordance with the teachings herein. The transmissions of the mobile station appear on the lower flow line 402, while the access point transmissions appear on the upper flow line 404. As mentioned, before the transaction illustrated herein, the mobile station and the access point will have established a reserved traffic flow, implying that the access point has some reserved resources to maintain the voice quality of the traffic flow. . That is, the access point will be able to service the flow in a timely manner so that the effect in real time of the flow is maintained. To avoid an overload scenario in a WLAN voice system, where an excessive number of high priority users could make it difficult for the system to satisfy the quality of service requirements, admission control for some services should be required, such as streaming audio and video in real time. For example, in an infrastructure based on a voice WLAN system, a mobile station (e.g., voice user) must configure a bidirectional traffic flow for voice using a known traffic specification, and the access point must recognize the admission of the flow of the mobile station. By admitting the flow, it is understood that the data flow will be a reserved traffic flow that has a unique traffic flow identifier. The reserved traffic flow will have a priority classification and will distribute a minimum amount of channel access time. During the connection configuration period, the UPSD power saving mechanism can be established by the mobile station implicitly by the use of a traffic specification reservation. In the frames with data content for the reserved traffic flow, the unique traffic flow identifier (TSID) will be included. The mobile station can select no energy saving operation, Legacy energy saving operation, or UPSD's current energy saving operation. After the traffic flow is admitted by the access point, the mobile station places the WLAN subsystem in a low power state. After the WLAN subsystem is placed in the low power mode, the mobile station preferably maintains a service interval synchronizer to maintain the flow operation in real time. Preferably, at the start of a service interval, the mobile station activates the WLAN subsystem, such as time 406. After that, during the time period 407, the mobile station begins to contend for the WLAN channel. The mobile station initiates the exchange by transmitting a query frame 408. The query frame can be a speech frame, which in the preferred embodiment contains a unique traffic flow identifier, and a speech data frame if the user of the mobile station is currently speaking, or if there is no data of voice to transmit currently, the query frame will be a null frame. The query frame will identify the reserved traffic flow and indicate the UPSD power saving mode. The query frame may also include signaling to indicate a desire for the access point to use the aggregate response method so that both reserved and non-reserved data can be received. Alternatively, the added response can be the default response mode. In the preferred embodiment, after the access point receives the query frame, it transmits an acknowledgment 410 in a period 412 of short interframe space time, which is a scheduled event, according to the IEEE specification 802.11. In response to the reception of the query frame, the access point transmits at least one response frame 416 to the mobile station, assuming that the access point has data placed in the aggregate temporary memory for the mobile station. Assuming that non-reserved data and reserved data exist in the aggregated time memory, at least a second response frame 418 will be transmitted. The access point will continue to transmit the response frames until the aggregate temporary memory is emptied, or, alternatively, after the expiration of a service period time. Each response frame includes an end of uplink service period (EUSP) bit, such as a MORE DATA bit (MORE_DATA) to indicate if there is more data coming from the access point, or if the present response frame is the last response frame for the service period. It is contemplated that the access point may not completely empty the aggregated time memory of the non-reserved data if the access point is currently providing the service to a high number of traffic flows reserved for another mobile station, and the provision of the Unreserved data may interfere with the supply of reserved traffic. The period of time between the receipt of the query frame and the transmission of the response frame may vary since the access point may have to finish serving another flow for another mobile station. In the preferred embodiment, there will typically be a period 414 of interframe space time back between the recognition and response frame. As soon as possible, the access point will acquire the WLAN channel and transmit the frame or response frames. However, the response frame is not sent with reference to some predetermined program. That is, the mobile station remains active to receive the response window for a period of time indeterminate. Of course, a reasonable maximum period of time could be observed to prevent the mobile station from waiting too long for a response frame or to remain active for too long. In case the maximum period occurs, the mobile station can take an appropriate action, such as consulting the access point a second time during the service period to check the status of the temporary energy saving memories and recover any frames that wait to be transmitted. The response frame will identify the flow of reserved traffic when it contains reserved data. If the access point has data in the reserved temporary memory associated with the reserved traffic flow, the access point will transmit a data frame from the temporary memory. If there is no data in the temporary memory added, the access point will transmit a null frame. Alternatively, if the added temporary memory is empty, then the acknowledgment 410 may indicate such an event. In the response frame there will be signaling information, such as an EUSP bit designed to indicate the end of the current service period, which may occur because there is no more data to transmit or because a time of maximum service period. In the preferred mode, a MORE_DATA bit can be used as the EUSP bit. If the MÁS_DATOS bit is cleared in the response frame, it indicates the end of the UPSD service period due to the successful transmission of the entire frame placed in temporary memory for the mobile station in the aggregate temporary memory, or at the end of the period of service due to time considerations. If the access point transmits a null frame in the response frame, the access point can also use the MORE_DATA bit to indicate that there is no more data and signal that the present service period has ended. If the reserved temporary memory has only one frame of data placed in temporary memory, it will transmit that data frame, and in a similar way it will set the MÁS_DATOS bit to indicate that there is no more data if the added temporary memory is empty, otherwise the data not reserved in the aggregated time memory will also be transmitted to the mobile station. In response to receiving the response frame, in the preferred embodiment, the mobile station transmits a recognition 420 in a short period 418 of interframe space time. If the response frame indicates the end of the current service period, the mobile station then places the WLAN subsystem in a state low energy after receiving the response frame in time 422. Referring now to Figure 5, an interval synchronizer diagram 500 and service inquiry for use with the invention is shown. Since the mobile station places the WLAN subsystem in a low power state, the WLAN subsystem can not receive signals from the access point. Therefore, to ensure the real-time quality needed for some media streams, such as voice and video, the mobile station must maintain the programming. The programming is performed in accordance with a service interval 502, which is a period of time equal to the real-time duration of a data frame in the traffic flow under consideration. In the preferred embodiment, for real-time voice applications that require telephony quality, the service interval is approximately 20 milliseconds, but may vary with the application and other parameters such as the vocoder rate. That is, a data frame contains approximately 20 milliseconds of voice data, producing a new frame every 20 milliseconds. The controller of the mobile station turns on the WLAN subsystem at the start of a range 503 of service. At the same time, a window synchronizer is started to synchronize a query window time period 504. If, after turning on the WLAN subsystem, there is data associated with the present traffic flow reserved to be transmitted, the WLAN subsystem will immediately begin to contend for the WLAN channel to transmit a query frame including the data. However, if no data is currently available after turning on the WLAN subsystem, the WLAN subsystem waits for the window synchronizer to proceed. If before the expiration of the window time period (506), the voice processor delivers a data frame to the WLAN subsystem that is associated with the reserved traffic flow, the WLAN subsystem immediately begins to contend for the channel of WLAN to transmit the data in a query frame. However, if at the expiration of the window time period at 506 no data has arrived, the WLAN subsystem contends for the WLAN channel and transmits a null frame as the query frame. It will be appreciated that the window synchronizer will have a duration that is significantly shorter than the service interval time period. To ensure traffic priority admitted or reserved, the containment scheme used by the mobile stations is modified based on the priority of the data that is sent.

Typically, containment in WLAN systems is done by determining if the WLAN channel medium is inactive or busy. If the medium is inactive, then there is currently no traffic on the channel. If the medium is busy, a station is currently transmitting. There are a variety of ways in which a station can determine if the medium is inactive or busy, such as, for example, channel carrier detection, or energy detection. To detect the carrier, the WLAN device tunes its receiver to the channel carrier frequency and "listens" to a carrier. The presence of a carrier indicates that the channel is currently in use. Similarly, if the energy in the channel exceeds a pre-selected threshold, then it is considered that the medium is being used by another station. When the channel is busy, the WLAN device waits for a pseudo-random time period in a range of time, and tries again. This is referred to as "wait". At the end of the timeout period, the WLAN device sends again the channel carrier frequency, until the WLAN device finds the channel that is free of carrier for a short preselected period of time. After finding the available channel, the WLAN device can start transmitting data. There are several schemes where, as the WLAN device repeatedly finds the busy channel, it reduces the waiting time range. In the preferred embodiment, when priority is given to applications in real time, the range of timeout period used in contention is initially shorter than that used in the containment of unreserved data traffic flow. By using shorter waiting periods for reserved traffic flows, these flows will generally acquire the channel before the non-priority traffic. In the UPSD power saving mode of the invention after the mobile station transmits the query frame, the mobile station remains awake until the access point transmits a response frame. The response frame is not transmitted according to a particular program. Instead of the access point ending other transactions with which it is connected currently, if there are any, and then transmit the frame or response frames to the mobile station. The access point provides' service to the mobile station as soon as possible after receiving the query frame, but not as a programmed response, or in a predetermined time interval. One benefit of this unscheduled energy saving mode of operation is that the mobile station does not have to transmit a frame to indicate to the access point that the mobile station is transitioning to the low power mode - it is assumed due to the presence of a TSID. In the energy saving mode of the prior art, such as LGCY5 and LGCY6, the mobile station would frequently have to make three transmissions to complete a transaction or service period with the access point before placing the WLAN subsystem back into the low energy status Using the present non-programmed energy saving mode of the invention, the mobile station transmits a query frame, and preferably a recognition frame after receiving the response frame from the access point. When transmitting the query frame, the mobile station provides a TSID to indicate the use of the operation mode of the UPSD. The access point always it will respond to a query frame when the TSID is used, and will treat the mobile station as if it were in the low power mode during the time when the access point is not responding to the query frame. Therefore, the access point will not treat the mobile station as if it were in a fully active state unless the mobile station explicitly requests to exit UPSD power saving mode, either by transitioning to active mode or exiting mode. of UPSD completely by modifying its reservation of resources in order to disable the UPSD or terminate a reserved traffic flow. Referring now to Figure 6, a transition diagram of states se 600 is shown, illustrating how the mobile station informs the access point about the energy saving mode that the mobile station is using. Essentially there are three states; energy saving 602, active 604, and UPSD 605. From the active state, to make the transition to sleeping state, the mobile station transmits a frame 606 to the access point. The frame includes a header 608 and a payload 610 which may contain data or may be a zero payload. Inside the header are the bits used to indicate the state of energy saving. According to the invention, there is a bit 614 of type to indicate the type of frame that is the present frame, such as a data frame, a null frame, a recognition frame. The header may include a traffic specification identifier (TSID) 613 to identify a particular reserved traffic flow or to which frame it belongs. When the mobile station is making a transaction with the access point for a reserved traffic flow, the TSID will be used. In the preferred embodiment, the header also includes a legacy power saving bit 612 to indicate the use of a legacy power saving mode as an alternative to the present energy saving mode, such as those shown in Figures 4B and AC. Setting any of these bits tells the access point that the mobile station is using the corresponding power saving mode. Clearing the bits indicates that the mobile station is in the active state. In a legacy power saving mode, such as LGCY5 or LGCY6, the mobile station must transition from the power saving state to the wake state each time a transaction is made with the access point. And how much does it end with a transaction? for a given cycle, but tell the access point that it is transitioning from the active state to the energy saving state. However, according to the invention, using the power saving mode of UPSD allows the mobile station to perform the transaction with the access point, without having to inform the mobile station about an explicit change of state. As long as the TSID is present in the header, the state of the legacy power management bit is irrelevant to receive traffic from the TSID from the access point. Referring now to Figure 7, a flowchart 700 is shown illustrating a method used by a mobile station to utilize the unscheduled power saving mode of supply, according to the invention. At the start (702) of the method, the mobile station and the access point are switched on and are ready to communicate. Then, a call needs to be configured (704). The call is essentially a data session with guaranteed resources in order to ensure the real-time integrity of the information handled during the pending state of the data session. The call can be initiated by the mobile station or by the access, as is known in the subject. The mobile station and the access point negotiate the quality of service to be used in association with the call, and during the negotiation the mobile station indicates the use of the UPSD mode. When configuring the call, the access point supports the flow of call traffic as a reserved traffic flow. Once the call is configured, the mobile station initiates a synchronization mechanism, such as the service interval interrupt and the query window synchronizer (706), as described with reference to Figure 5, herein. After admitting the reserved traffic flow and informing the access point that the mobile station will use the power saving mode of UPSD, the mobile station places the WLAN subsystem in a low power state (708). The low power state reduces the power consumption by the WLAN subsystem, but also renders the transceiver inoperative. The use of low energy modes is often referred to as putting the system in "sleep" mode. The mode of is carried out by removing energy from some components of the system. Once the WLAN subsystem is in the low power mode, the mobile station waits until the arrival of an associated data frame with the reserved traffic flow coming from the voice processor, or other real-time media processor, or the occurrence of a service interval event, such as an interruption (710). When new data is associated with the arrivals of reserved traffic flows, or when the service interval event occurs, the mobile station turns on the WLAN subsystem (712). Then, the mobile station begins a frame exchange with the access point by initiating a frame exchange process (714), for example, by calling a software subroutine to complete a service period. The frame exchange process is carried out in accordance with the process described with reference to Figure 4. Once the frame exchange ends, the mobile station checks whether the call has ended (716). If the call continues, then the process returns to establish the service interval interrupt (706). If the call has ended, then the call is dropped and the resources are released at the access point (718) which terminates the process (720). Referring now to Figure 8, a flow diagram of a mobile station frame exchange process 714 is shown, in accordance with the invention. At start 800, the mobile station checks whether there is data currently pending for the flow of reserved traffic coming from voice processors or other media processors in real time. If not, then the mobile station waits for the synchronization of the query window to be synchronized with a query window. The mobile station also contends for the WLAN channel during this time. Once the channel is acquired, the mobile station transmits a query frame (802). The query frame will contain data if the data is pending or if the data arrives during the pending state of the window synchronizer, otherwise the query frame will be a null frame. The query frame identifies the reserved traffic flow and the UPSD mode. The reserved traffic flow is preferably identified by its TSID, and the presence of the traffic flow identifier indicates to the access point that the mobile station is using the UPSD power saving mode. In one embodiment of the invention, the aggregate response from the access point is the default mode, but the aggregate response mode may also be selectable, and the desire to receive an aggregate response may be indicated in the query frame.

In the preferred mode, the access point transmits an acknowledgment that is received by the mobile station (803). If the acknowledgment is not received (804), the mobile station can go on hold, afterwards retransmitting the query frame.

After transmitting the query frame, and in the preferred mode, it receives the acknowledgment, the mobile station then waits for the access point to respond. Since the response is not programmed, the waiting time is variable, although the mobile station may have a preselected maximum period of time to wait before undertaking an error procedure, assuming that an access point failure must respond. However, assuming normal operation, the access point transmitted an aggregation of response frames that will be received by the mobile station (806). When transmitting the data from the aggregated temporal memory, the data pertaining to the traffic flow identified by the TSID used by the mobile station in the query lock may first be transmitted, before the non-reserved data, in the aggregate response. Again, in the preferred mode, the mobile station will transmit a recognition to assure the access point a successful supply. After receiving the response frame, the mobile station checks the EUSP bit to see if the UPSD service period has ended. In the preferred mode, the MÁS_DATOS bit can be used to signal when more data is coming from the access point (808), and when it is established it indicates that the service period continues until at least one or more response frames are resided. If the MORE_DATA bit indicates that subsequent frames are arriving, then the mobile station remains here to receive them as it did for the first response frame. It is contemplated that the subsequent response frames may contain data for a different reserved traffic flow also in use by the mobile station, or for the present reserved traffic flow. Once a response frame is received indicating that more compliant data is not arriving from the access point, the process terminates (810) and the mobile station places the WLAN subsystem in the low power mode. Referring now to Figure 9, there is shown a flow chart of a method for temporarily storing data at an access point, according to the invention. At the start (902) of the method, the access point has admitted a reserved traffic flow to establish a call with a station mobile. The data packets arrive from a network at the access point that are designed for the mobile station. As the data packets arrive, the visit access point if the data packet is intended for a mobile station that is currently in an energy saving mode (904). If the mobile station for which an incoming packet is destined is not currently in an energy saving mode, the access point transmits the packet (906) to the mobile station. If the mobile station is currently in an energy saving mode, then the access point must determine whether the mobile station is using a legacy power saving mode or the current unscheduled power saving mode (908). ). If the mobile station is using a legacy power saving mode, then the access point places the packet in temporary memory in a non-reserved temporary memory (910) and will signal the mobile station about the status of its temporary memory, for example, in a periodic beacon frame transmitted by the access point. If the packet is associated with a supported flow for a mobile station using the UPSD mode, then the packet is stored in a reserved temporary memory (912) from UPSD. In the preferred embodiment, the access point here applies a seniority classification policy with the temporary memory of UPSD only the two most recently received packets are kept in the temporary memory. A new packet is reached and there are already two in the temporary memory of UPSD, then the oldest packet placed in temporary memory is discarded and the newest packet is placed in temporary memory. Referring now to Figure 10, there is shown a flow diagram of a method for removing data from the access point for use in an unscheduled energy saving mode 1000 according to the invention from the temporary memory. At the start (1002) of the method, the access point has admitted a reserved traffic flow to establish a call to a mobile station. The method proceeds when the access point receives a query frame (1004) from the mobile station using the UPSD mode. In an alternative embodiment of the invention, where the aggregate response is selectable by the mobile station, and not the default response mode, the access point verifies the aggregate response signaling bits (1005) in the query frame to see if the mobile station has selected the aggregate response mode. If the aggregate response mode is selectable, and the mobile station has not selected the aggregate response mode, the access point, in response to the query frame, verifies the temporary memory associated with the reserved traffic flow indicated in the field TSID of the query frame transmitted by the mobile station (1006). If there is no data in the temporary memory of UPSD, then the access point acquires the WLAN channel and transmits a null frame (1008) indicating that there is no more data. If there is data in the temporary memory of UPSD, then the access point prepares the data for transmission. When there is only one remaining data frame, the access point sets the EUSP bit, or alternatively clears the MORE_DATA bit to indicate that there is no more data after the present response frame, acquires the WLAN channel, and transmits the frame of response. If there is more data to be transmitted, the EUSP bit is cleaned, or alternatively the MORE_DATA bit is set to indicate such an event. Then the WLAN channel is acquired by the access point, and the aggregate response frame is transmitted to the mobile station (1016). If the default mode is response supply added, or if the mobile station has selected the aggregate response mode in the aggregate signaling bit of the query frame, then the access point verifies if the added temporary memory has data (1018). If the added temporary memory is empty, implying that there is no reserved or reserved data for the mobile station, then the service period ends 1028 for the access point either by sending a null frame with the EUSP or MORE_DATA bit indicating that there is no data, or the absence of data can be indicated equivalently in the recognition frame in response to the query frame. Assuming that there is data in the aggregated temporal memory, the access point retrieves a data frame (1020) and checks whether the present data frame will be the last frame (1022). If the present frame will not be the last frame, the frame is transmitted without being indicated as the last frame (1026). If the present frame at 1020, 1022 is the last frame to be transmitted during the present service period, then the access point indicates it in the frame and transmits the frame (1024). Therefore, the invention provides a method for executing the energy saving operation in a wireless local area network (WLAN) by a mobile station while performing voice communications or other communications in real time. The method starts by admitting a flow of reserved traffic at the access point, which includes establishing a UPSD or temporary memory reserved at the access point to place in temporary memory the data corresponding to the flow of reserved traffic that is about to be transmitted to the station. mobile phone during the course of the call. The access point also has a temporary memory for the best effort or non-reserved data, and together with the two temporary memories form an aggregated time memory. Once a call is established, the WLAN subsystem of the mobile station is placed in a low power state. Subsequently, the method starts by waking the WLAN subsystem of the mobile station from the low power state in order to transmit data to the access point, if there is any data to be transmitted. Once the WLAN subsystem is turned on, the method starts by acquiring the WLAN channel between the mobile station and the access point, and by transmitting a query frame to the access point by the WLAN channel, the query frame identifies the reserved traffic flow. The acquisition of the WLAN channel is preferably done through containment protocols known, including the detection of carriers. The query frame can be a null frame if no data has arrived at the WLAN subsystem of the mobile station, but otherwise contains data derived from the call. In response to the transmission of the query frame, the mobile station begins to receive an aggregate response in the mobile station through the channel of WLAN The aggregate response is transmitted by the access point and can include both reserved and non-reserved data, and continues until the aggregated temporary memory is emptied or until the end of a service period time interval. Once the aggregate response has been received, the mobile station begins to establish the WLAN subsystem in the low power state. It should be noted that although the aggregate response is sent in response to the query frame, the aggregate response does not necessarily begin to transmit immediately. The access point may have other transactions that require the service before the aggregate response can be transmitted, therefore the aggregate response is transmitted in an unscheduled manner. In the preferred mode, the query frame and the response frame are both recognized by the respective receiver with a recognition at a specified time, such as, for example, a short inter-frame space as specified by the IEEE 802.11 standard. In addition, the aggregate response will be selectable indicating the desire to use the aggregate response mode in the query frame. The reception of the aggregate response may include receiving a header of a response frame having a clean EUSP bit, or alternatively 1 bit MORE_DATA established to indicate that a second response frame will subsequently be transmitted, and where the method further includes the reception of a second response frame in the mobile station. The mobile station may wake up in response to the presence of data received from a joy process or other media process in real time from the mobile station, or in response to a service interval interruption. After the occurrence of a service interval event, at the start of a service interval, for example, the mobile station starts executing the window synchronizer that has a duration shorter than the service interval. If the window synchronizer expires and there is no data yet, then the mobile station starts transmitting a null frame. The service interval is selected as the real-time duration represented by a Data Frame Although the preferred embodiments of the invention have been illustrated and described, it will be clear that the intention finds us limited. Various modifications, changes, variations, substitutions and equivalents may occur to those skilled in the art without being insulated from the spirit and scope of the present invention as defined or the appended claims.

Claims (10)

1. NOVELTY OF THE INVENTION Having described the invention as antecedent, the content of the following claims is claimed as property: CLAIMS 1. A method to execute an energy saving operation in a wireless local area network (WLAN) by a mobile station while executing voice communications, characterized in that it comprises: admitting a traffic flow reserved in an access point, including establishing a temporary memory reserved in the access point to place in temporary memory the data corresponding to the flow of reserved traffic to be transmitted to the mobile station; wake up a WLAN subsystem of the mobile station from a low power state; transmitting a query frame to the access point over the WLAN channel, the query frame identifying the reserved traffic flow and including an aggregation indicator; in response to the transmission of the query frame, receive an aggregate response in the mobile station by the WLAN channel, where the aggregate response it includes at least one data frame from a temporary memory added to the access point, the added memory to place both reserved and non-reserved data in temporary memory for the mobile station, and where the reception of the aggregate response continues until the memory temporary added is emptied or a period of time of service expires; and after receiving the aggregate response, establish the WLAN subsystem in the low power state.
2. 2. A method for executing the energy saving operation according to claim 1, characterized in that the aggregate response is transmitted in response to the bit added in the query frame.
3. A method for executing the energy saving operation according to claim 1, further characterized in that it comprises receiving a recognition frame in the mobile station from the access point via the WLAN channel in response to the transmission of the query frame .
4. 4. A method for executing the energy saving operation according to claim 1, further characterized in that it comprises transmitting a recognition frame coming from the mobile station to the access point through the WLAN channel in response to the reception of at least one response frame.
5. A method for executing the energy saving operation according to claim 1, characterized in that: receiving the aggregate response includes receiving a header from a first frame of the aggregate response that has a MÁS_DATOS bit set to indicate that subsequently a second response will be transmitted response pattern; the method further comprising receiving a second response frame in the mobile station.
6. 6. A method for executing the energy saving operation according to claim 1, characterized in that transmitting the query frame comprises transmitting a null frame.
7. A method for executing the energy-saving operation according to claim 6, characterized in that the transmission of the null frame is performed after the expiration of a window synchronizer initiated after the start of a service interval, defining the interval of service a real-time duration of a speech frame, the window synchronizer having a duration shorter than the service interval.
8. 8. A method for executing the energy saving operation according to claim 1, further characterized in that it comprises acquiring the WLAN channel after waking the WLAN subsystem, executed to the contender by the WLAN channel.
9. 9. A method for executing the energy saving operation according to claim 8, characterized in that contender for the WLAN channel is executed by carrier detection.
10. 10. A method for facilitating the operation of saving energy by an access point in a wireless local area network (WLAN) by a mobile station while executing voice communications, characterized in that it comprises: admitting a traffic flow reserved in the access point, including establishing a temporary memory reserved in the access point to place in temporary memory the data corresponding to the traffic flow reserved for transmitting to the mobile station, forming the reserved temporary memory and an unreserved temporary memory an aggregate memory at the access point where the non-reserved data is placed in temporary memory in the non-reserved temporary memory; receive a query frame at the point of access by the WLAN channel from the mobile station, the query frame identifying the reserved traffic flow; verifying whether the temporary memory added for data placed in temporary memory by being sent to the mobile station; and transmitting an aggregate response to the mobile station over the WLAN channel, the aggregate response being transmitted by the access point and including data in the aggregated time memory, continuing the transmission until the aggregate temporary memory is emptied or until a service time period.