MXPA06006969A - Hybrid power save delivery method in a wireless local area network for real time communication - Google Patents

Abstract

A mobile station establishes a schedule by which data is exchanged with an access point. The schedule allows the mobile station to use a low power mode (608) at times outside of the scheduled service periods. However, the mobile station may occasionally need to retrieve additional data from the access point, or transmit additional data to the access point, and so initiates an unscheduled service period to do so (614).

Description

METHOD OF SUPPLY D? SAVINGS D? ENERGÍA H BRIDO? N A WIRELESS LOCAL AREA NETWORK FOR COMMUNICATION? N REAL TIME FIELD OF THE INVENTION This invention relates generally to wireless local area networks, and more particularly to energy saving methods for reducing energy consumption in a mobile station while linking to a time-detected communication activity.

ANTECED? NTES D? THE INVENTION Wireless LAN (WLAN) systems that provide wireless bandwidth access have experienced a dramatic increase in popularity in recent years. Since the main application of these systems has been to provide network connectivity to portable and mobile devices that run applications such as, e.g., e-mail and web browsing, there has been tremendous and growing interest in the isochronous support services, such as telephony service and streaming video streaming.

One of the key issues faced by wireless system designers when they consider voice services and other services detected over time in a WLAN connection, such as the one described by the IEEE 802.11 specification, is the power consumption of portable devices. . For example, to provide competitive talk time and standby time, compared to digital cellular or wireless devices, it is necessary to conserve power during voice calls. Several organizations have proposed energy efficient operation through transmission power control and physical layer speed adaptation for systems that are supported in a centrally controlled containment free channel access scheme. However, such descriptions can be complex to implement and may not provide the energy savings required to justify the complexity. The 802.11 standard defines the procedures that can be used to implement the management of energy in a portable device during periods of inactivity. In particular, three different building blocks are provided to support the energy savings: a Service Procedure, an Inactive Procedure, and an Energy Saving Interrogation Procedure (PS-Poli). A mobile client voice station (mobile station) can combine these building blocks in various ways to support energy management for different applications. Active procedure: There are generally two reasons for the mobile station to be active, namely to transmit the pending data or to retrieve the data stored in the buffer of the fixed station serving the mobile station, known as a data point. access. The attention status for transmitting the data is a direct operation, directed by the mobile station. The decision to be active and receive the data is also made by means of 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 the inactive mode to the active mode, it modifies the access point by sending an uplink frame with the energy saving bit (PS) set to active. Following said transmission, the mobile station remains active so that the access point can subsequently send any of the downlink frames stored in the buffer. Inactive Procedure: Similar to the active procedure, a mobile station in active mode needs to complete a successful frame exchange sequence initiated in the mobile station with the PS bit set in the inactive state to transition to the inactive mode. Following this frame exchange sequence, the access point stores in the buffer all the downlink frames for this mobile station. Energy Saving Interrogation Procedure (PS-Poll): Instead of waiting for the access point to transmit the downlink frames stored in the buffer, a mobile energy saving station can request an immediate supply from its access point using an energy saving interrogation frame (PS-Poll). Upon receiving this energy saving interrogation (PS-Poll), the access point can immediately send a downlink frame stored in the buffer (immediate data response) or simply send a message of recognition and response with a frame of data later (delayed data response). In the case of immediate data response, a mobile station can remain in an inactive state after this frame exchange has been completed, since it is not necessary for the mobile station to transition to the active state since the access point can only send a downlink frame stored in the buffer after receiving an energy saving interrogation (PS-Poll) from the mobile station. On the other hand, in the case of delayed data response, the mobile station has to transition from the active state until it receives a downlink frame from the access point. The architecture of a single WLAN system for companies in Figure 1 is shown. Referring now to Figure 1, there is shown an overview of the system block diagram 100 of a typical enterprise WLAN system. It includes an infrastructure access network 101, consisting of an Access Point 102 and the mobile stations such as a data station 104 and a voice station 106. The mobile stations are connected to the access point through a data link. WLAN radio 108. The access point is connected to a distribution network, including the data and voice gateways 110, 112 respectively, through a switch 114. The voice station runs an Internet Voice Transmission (VoIP) application ), which establishes a port-to-port connection with the voice gateway, representing 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 gateway through the access network and connect, 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 priority contention. The characteristics of voice transmission over the Internet (VoIP) make it apply only voice in WLAN applications for energy saving operation. In particular, VoIP applications periodically generate the speech frames, wherein the intermediate time of arrival between frames depends on the voice encoder selected for their application. The process of encapsulating voice frames in IP packets is commonly referred to as packetization, which is often assumed to happen once every 20 milliseconds. A typical VoIP conversion involves a bi-directional constant bit rate flow of VoIP frames, including uplink flow of the portable telephone to a voice gateway and downlink flow in the opposite direction. Since the station generally knows in advance the frame arrival speed, the delay, and the broadband requirements of its voice application, it can reserve resources and set the energy handling for its voice flows according to the access point. A mobile station can renounce the energy saving mode, and remain in active mode, always ready for the downlink voice transmission. In this case, the access point can transmit the downlink voice frames as they arrive. However, if it is desired to save energy, the mobile station can employ the energy saving building blocks described above for the active state, exchange the VoIP frame with its access point, and return to the inactive state. In a shared media network, such as the access network shown in Figure 1, it is important to prioritize VoIP traffic over traffic by requesting only the best effort delivery, such as traffic generated by the application that can be adapted to the amount of broadband available on the network and does not request or require a minimum performance or delay. By giving it priority, it allows the system to minimize the delay experienced by the delay detector traffic. A contention-based channel access scheme has been specified that offers priority access called Enhanced Distributed Channel Access (EDCA) in the IEEE 802. lie draft, and is available for VoIP applications. It is based on the Multiple Access Carrier Detector with Anti-collision mechanism (CSMA / CA) defined in 802.11. The stations with voice frames to send must first detect the channel that will be activated, before the transmission. If the channel has been inactive for at least one specific period, called an interframe arbitrage space (AIFS), the mobile station can immediately initiate its transmission. Otherwise, the mobile station goes back and waits for the channel to be inactive for a random period, which is equal to an AIFS period plus a value evenly distributed between zero and a containment window period (CW) value. The CW is also limited by the Minimum containment window (CWmin) and the Maximum containment window (CW ax). EDCA provides priority access control by adjusting containment parameters: AIFS, CWmin, and CWmax. By selecting different values of AIFS, CWmin, and CWmax for different access categories, the priority to access the medium can be regulated and differentiated. Generally, small values of AIFS, CWmin, and CWmax result in higher access priority. It is possible for a mobile station to use the information such as the intermediate arrival time of the downlink voice frames, together with an energy saving mechanism, to place itself in an inactive state between the two consecutive voice frames. Currently, there are energy saving procedures described in several documents and specifications related to WLAN.

The energy management mechanism of the first prior art uses a bit in the packet header. The bit is designated as an energy management bit (PM) to signal the change of the energy status of the mobile station to the access point. First, a mobile station performs the transition from the inactive mode to the active mode with an uplink data frame to be transmitted by setting the PM bit as active in an uplink voice frame to notify the change of its status of Energy. Knowing that there will be a corresponding downlink frame stored in the buffer at the access point, since the downlink and uplink voice coder 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 subsequently sends the downlink frames stored in the buffer memory to the mobile station. In the last downlink frame, the access point sets the "more data" bit to FALSE to communicate the end of the downlink transmission. Finally, the mobile station needs to complete a successful frame exchange sequence initiated at the station with the PM bit set to an inactive state to transition to the idle mode (e.g., an uplink frame, or a Null frame, if not there is some uplink data frame to transmit, with the PM bit set in the inactive state). In the following context, the mechanism based on the PM bit is referred to as LGCY6 in the art. A second power management mechanism uses a PM-Poll frame to request the downlink frames. Instead of waiting indefinitely for the access point to provide the downlink transmission, the PM-Poll-based mechanism uses the PM-Poll frame to retrieve the downlink frame stored in the buffer from the access point. First, a mobile station transitions from the active mode until it has an uplink data frame to transmit. The mobile station sends the uplink transmission later. Similar to the mechanisms based on PM-bit, the access point establishes the field of more data to indicate the presence of any downlink transmission stored in the internal memory. If the bit plus da cough is TRUE, the mobile station will continue to send a PM-Poll frame to retrieve the downlink frame stored in the buffer. Unlike the mechanism based on PM-bit, a mobile station can remain in an inactive state since the access point responds to the PM-Poll with an immediate data frame. In the following context, reference is made to the mechanism based on PM-Poll as LGCY5 in the art. There are a couple of problems to support efficient VoIP power operation using the current WLAN power saving mechanisms. First, the mechanism based on the PM bit is somewhat inefficient because, for example, the 802.11 standard only currently offers one way for the mobile station to transition to the idle mode, which is by initiating a frame exchange sequence with the PM bit set to inactive mode. As a result, an extra mobile station that has initiated the frame exchange by bi-directional voice transfer is required 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 the voice application with the 20 ms frame and the 8 Kbps voice coder), the overhead incurred through the extra frame exchange could be as high as one third of the traffic between the mobile station and the access point. The significant overload results in the inefficiency in both concepts, the power consumption and the PM-Poll-based mechanism of the system capacity, since a mobile station does not know the priority of the downlink frame stored in the buffer memory, sends the PM-Poll frame 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, voice traffic using the best effort priority with voice traffic, and a mobile station retrieves the downlink voice traffic using an energy saving interrogation frame for the same priority as Data traffic, the system will not have the ability to protect voice traffic from the delays associated with a better congested effort supply system. The legacy energy saving methods may also require an interrogation or uplink frame to retrieve each of the frames stored in the buffer for the downlink, or require immediate response from the access point for a given uplink frame. One method of providing a particular quality of service is to use the scheduled service periods at regular intervals for a given mobile station. Reference is made to this programmed mode of energy saving supply as an automatic energy saving (APSD) supply. The mobile station is active at regular intervals and listens to the channel. The access point to the service period is synchronized, and transmits the data to the scheduled period. In this way, the mobile station can put the WLAN sub-system in an inactive state during the periods between scheduled service intervals. However, this method limits the flexibility of the WLAN channel since the mobile station does not have the ability to deviate from the program. Therefore, due to these deficiencies of the prior art, a reliable power management protocol is necessary in a WLAN system that allows the mobile station, with active voice sessions, to enter and exit efficiently from energy saving mode without excessive overload and maintain quality of service in the presence of the lowest priority traffic.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows an overview of the block system diagram of a typical enterprise WLAN system that 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 chart illustrating an overview of the flow of traffic between a mobile station and an access point in a WLAN system to support voice quality communication and that uses both scheduled and unscheduled transactions of according to the invention. Figure 5 shows a flow chart illustrating an overview of the flow of traffic between a mobile station and an access point in a WLAN system to support voice quality communication during an unscheduled negotiation, according to the invention. Figure 6 is a flow chart illustrating a hybrid method for developing the energy saving operation in a mobile station of a WLAN, according to the invention. Figure 7 shows a flow diagram of a frame exchange procedure of the mobile station during an unscheduled service period, according to the invention.

Figure 8 shows a flow diagram of a storage method in the data buffer in an access point, according to the invention.

DETAILED DESCRIPTION D? THE INVENTION Since the specification concludes with the claims defining the features of the invention, to which reference is made as novel, it is believed that the invention will be better understood, taking into consideration the following description in conjunction with the figures, wherein out the numerical references. The invention solves the problems associated with the prior art method of the scheduled operation allowing a more flexible use of scheduled and unscheduled transactions. The mobile station first establishes a scheduled transmission to be used in association with a high priority access category stream, such as a real-time voice call or a video transmission, for example. Consequently, the mobile station enters a low energy mode, and expects it to initiate a scheduled service period. Scheduled service periods are presented at regular intervals and have a predetermined duration. Occasionally, the access point may have to end the service period before data stored in the buffer can be transmitted. At the end of the scheduled service period, the mobile station can receive the access point notification that the access point still has the data stored in the buffer for the mobile station, and can indicate the type or access category of the mobile station. data that is stored in the buffer at the access point. At the end of the scheduled service period, the mobile station can place its WLAN components in a low power mode. Subsequently, the mobile station may initiate an unscheduled service period before the next scheduled service period retrieves the remaining data, if conditions permit. For example, before deciding to start an unscheduled service period, the mobile station can check its battery status to see if there is sufficient power balance, or can determine, based on the information provided by the access point, that the The remaining data at the access point are from an access category that requires immediate attention. The mobile station may also use unscheduled negotiation for low priority service data flows.

Referring now to Figure 2, there is shown a schematic block diagram 200 of a mobile station for use in a WLAN system, according to the invention. The mobile station comprises a speech processor 202 for processing speech signals, including the transformation signals between the digital and analog forms. The speech processor is operatively coupled to a WLAN sub-system 204. The WLAN sub-system contains the data buffers and the radio hardware for sending and receiving information on a wireless radio frequency link through an antenna 206. The speech processor converts the digital voice and audio data received from the WLAN sub-system in analog form and reproduces them in a transducer, such as a loudspeaker 208. The speech processor also receives the analog voice and the speech signals. audio from a microphone 210, and converts them to digital signals, which are sent to the WLAN sub-system. Preferably, the speech processor also develops speech coding and decoding, using, for example, linear summation vector encoding techniques known in the art. The use of voice coding allows the compression of voice data. In addition to the voice procedure, the mobile station may have other media processors, summarized as window 212, which may include regular data applications such as e-mail, for example. In the same way, these other data processors are operatively coupled to the WLAN sub-system via bus 214, for example. As the data arrives at the WLAN sub-system, it is stored in a WLAN buffer 216, and subsequently it is packaged to be transmitted on the IP networks. Each processor that sends the data to the WLAN subsystem indicates the type of data, and formats the data its transmission, indicating the type of data in the frame. All data processors and the WLAN sub-system are controlled by means of a controller 218. The controller directs the power saving operation of the WLAN sub-system, placing it in the lower power states when appropriate and energizing them when necessary. time to transmit or receive the data. Referring now to Figure 3, a schematic block diagram 300 of an access point for use in a WLAN system according to the invention is shown. A WLAN transceiver 302 develops the radio frequency operations necessary to communicate with the mobile stations in the vicinity of the access point through an antenna 304. The access point to the networks is connected through a network interface of gateway 306, typically through a fixed line 316, such as a coaxial cable, for example. The data received at the access point is immediately transmitted from the mobile station to the gateway to be routed to the appropriate network entity. The data received at the access point can be treated from the network that is intended for a mobile station according to one of at least three classifications. First, the mobile station may be in active mode, in which case, the data is stored in the buffer only until it can be transmitted. In which case, the intention is not to further delay the transmission to the mobile station as necessary, and the data for a mobile station of this classification is transmitted typically transmitted using a row discipline based on priority. A second category of the energy saving state of the mobile station is a mobile station in an inherited or non-reserved energy saving mode. For this second classification, a buffer 308 stores the data in a non-reserved data buffer 310 until it receives it from the gateway 306 via a bus 318. The non-reserved data is data that does not belong to a transmission of reserved traffic. When the mobile station in particular, for which the non-reserved data is stored in the buffer, it transmits to the access point, either an energy saving interrogation frame of non-reserved data or a frame that makes the transition from the mobile station to the active state, the access point will respond by transmitting the non-reserved data to the sequential interrogation station from the non-reserved data buffer. The form of supply can be controlled by means of the mobile station, where only the non-reserved data is provided in response to a specific interrogation or sequential interrogation frame, or it can be provided according to an agreement and regular program in intervals. In a third energy saving classification, the access point can receive the data, since said reserved data is intended for a mobile station using the current hybrid energy saving method. The reserved data is data belonging to a reserved traffic transmission. For the reserved flow data, the buffer manager 308 stores the data in a reserved buffer, such as the reserved buffer 312. The reserved buffer means that the buffer is used to store the data belonging to the buffer to a reserved traffic transmission, such as a voice call in real time. Attempts are made to transmit most of the reserved data during scheduled service periods that occur at regular intervals.

Although two separate physical buffers are illustrated in the present invention, those skilled in the art will understand that a variety of buffering techniques can be used to store non-reserved and reserved data separately, without requiring memory physical intermediates separately. Additionally, since the access point will respond to the sequential interrogation frame with an aggregate response, the non-reserved data buffer and the reserved buffer may be treated as an aggregate buffer 309. In one embodiment of the invention, when the The mobile station interrogates the access point sequentially during an unscheduled service period, the access point empties the aggregated buffer by transmitting all the aggregate data stored in the buffer to the mobile station. In other methods of saving energy, the access point complies with an old policy to prevent storing too much reserved data in the buffer at the access point. However, using the current hybrid method, the access point can be supported in the mobile station by initiating unscheduled negotiation to retrieve the remaining reserved data instead of discarding the reserved data, as is done in other methods.

A controller 3.14 monitors the operation of the buffer manager 308, gateway 306, and transceiver 302. The controller also manages the resource management and controls the resources in such a way that the quality of service can be ensured as necessary for the transmissions of reserved traffic. The controller is operatively coupled to a memory 315, which it uses to track call status, energy saving states of the mobile station, and other parameters. With reference to Figure 4, a flow chart 400 is shown which illustrates an overview of the flow of traffic between a mobile station and an access point in a WLAN system to support voice quality communication and use both scheduled transactions and not programmed, according to the invention. The mobile station and the access point are linked in scheduled transactions at regular intervals 402. Before starting a scheduled service period, the mobile station exits the low power mode by energizing the WLAN sub-system. The program is remembered and predetermined by the access point and the mobile station. The access point will typically initiate the transmission of data to the mobile station, if data exists to transmit, assuming that the mobile station is active and is receiving the data. It is contemplated that the access point may end a negotiation with another mobile station at the start of the scheduled service period, so that the mobile station simply expects its data to appear in the WLAN channel. At the end of the scheduled service period, the access point transmits a frame indicating whether or not the access point still has data stored in the buffer at the access point for the mobile station that might not be transmitted within the duration of the period of scheduled service. Such indication is easily provided in a control field of the packet header of the frame. The control field may include a bitmap that describes the access categories and whether or not data exist for each of the access categories. In this way, the control field allows the mobile station to determine the priority of the remaining data at the access point. In response to the presence of remaining data at the access point, the mobile station may initiate an unscheduled service period 404, if conditions permit. Subsequently, unscheduled negotiation can be used to retrieve the remaining data, as well as the transmission data to the access point to route them. The access point may limit the number of unscheduled service periods that a mobile station may initiate between the scheduled service periods.

With reference to Figure 5, there is shown a flow diagram 500 which illustrates an overview of the flow of traffic between a mobile station and an access point in a WLAN system during an unscheduled service period initiated by the mobile station between the scheduled service periods. The traffic flow typically includes the reserved data, this means that the mobile station and the access point have negotiated a priority and average time for the transmission of reserved traffic 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 transmission or access category. With voice traffic, since it occurs in real time, you want to establish a traffic transmission reserved for communication. The system carrying out the flow shown in the present invention in Figures 4-5 can be developed by means of a system utilizing system and configuration components similar to those shown in Figures 1-3 with control software designed in accordance with with the teachings of the present invention. The transmissions of the mobile station appear in the lower flow line 502, while the access point transmissions appear in the upper flow line 504. As mentioned, prior to the negotiation illustrated in the present invention, the mobile station and the access point will have established a reserved traffic transmission, this means that the access point has reserved certain resources to maintain the voice quality of the traffic transmission. That is, the access point will generally have the capacity to provide flow service in a manner by time, so that the real-time effect of the flow is maintained. To prevent an overload scenario in a WLAN voice system, where an excessive number of high priority users could make it difficult for a system to satisfy the quality of service requirements, admission control for certain services, such as transmission, should be required. of video and voice in real time. For example, in an infrastructure based on the voice WLAN system, a mobile station (e.g., a voice user) should establish a bi-directional traffic flow for voice using a known voice application, and the access point should recognize the admission of the flow for the mobile station. Admitting the flow means that the data flow will be a reserved traffic transmission that has a unique traffic transmission identifier. Reserved traffic transmission will have a priority classification and will distribute a minimum amount of channel access time. During the period of the establishment of the connection, the programmed energy saving mechanism can be established by means of the mobile station, implicitly by the use of a traffic specification reservation. In frames containing data for the transmission of reserved traffic, the unique traffic transmission identifier (TSID) shall be included. The mobile station may select no energy saving operation, legacy energy saving operation, programmed energy saving operation only, or the current hybrid energy saving operation. After the access point supports the flow of traffic, the mobile station places the WLAN sub-system in a low-energy state. After the WLAN sub-system is placed in a low power mode, the mobile station maintains a service interval timer to maintain real-time operation of the flow during the scheduled service periods. However, if the data remains at the access point after a scheduled service period, the mobile station may choose to initiate an unscheduled service period. At the beginning of an unscheduled service period, the mobile station activates the WLAN subsystem at time 506. After which, during period 507, the mobile station initiates contention for the WLAN channel. The mobile station initiates unscheduled negotiation by transmitting a sequential interrogation frame 508. The sequential interrogation frame may be a speech frame, which in the preference mode contains a unique traffic transmission identifier, and a data frame of voice in case the user of the mobile station is currently speaking, or in the absence of any voice data to currently transmit, the sequential interrogation frame will be a null frame. The sequential interrogation frame will identify the transmission of reserved traffic. The sequential interrogation frame may also include signaling to indicate that it is desired for an access point to use an aggregate response method, such that both data, not reserved and reserved, may be received from the access point. Alternatively, the aggregate response can be the default response mode. In the preference mode, after the access point receives the sequential interrogation frame, it transmits an acknowledgment 510 within a short intermediate frame space period 512, which is a scheduled event, according to the IEEE 802.11 specification. In response to the reception of the sequential interrogation frame, the access point transmits at least one response frame 516 to the mobile station, assuming that the access point has added the data stored in the buffer to the mobile station. Assuming that both data, not reserved and reserved, exist in the aggregate buffer, at least a second response frame 518 will be transmitted. The access point will continue to transmit the response frames until the aggregate buffer is empty, or, alternatively, in case the access point should perform other scheduled tasks. Each response frame includes an end of the uplink service period (EUSP) bit, such as a MORE_DATA bit (MORE_DATA) to indicate whether or not there is more data coming from the access point, or if the current response frame is the last response frame for the service period. It is contemplated that the access point may not be able to completely empty the aggregate buffer of the non-reserved data if the access point is currently providing the service for a large number of traffic transmissions reserved for another mobile station, and that the provision of Unreserved data may interfere with the supply of reserved traffic. The period between the reception of the sequential interrogation frame and the transmission of the response frame may vary as the access point has the possibility of terminating another flow for another mobile station. In the preference mode, there will typically be an intermediate frame space of response return 514 between the acknowledgment and the response frame. As soon as possible, the access point will acquire the WLAN channel and transmit the response frame (s). However, the response frame is not sent with respect to any predetermined program. That is, the mobile station keeps the WLAN sub-system powered for an indeterminate period. Of course, a reasonable maximum period could be observed to prevent the mobile station from waiting too long for a response frame or to remain active for a long time. In the event that the maximum period occurs, the mobile station can take the appropriate action, such as sequentially polling a second time to the access point during the service period to verify the status of the energy saving buffers and recover any plot that is waiting to be transmitted. The response frame will identify the transmission of reserved traffic when it contains reserved data. If the access point contains data in the reserved buffer associated with the transmission of reserved traffic, the access point will transmit a data frame from the buffer. If there is no data in the aggregate buffer, the access point will transmit a null frame. Alternatively, if the aggregate buffer is empty, then the 510 acknowledgment can indicate this. In the response frame there will be signaling information, such as an EUSP bit designated to indicate the end of the unscheduled service period due to the successful transmission of the entire frame stored in the buffer for the mobile station in the aggregate buffer, or the end of the unscheduled service period due to time considerations. If the access point transmits a null frame in the response frame, the access point may also use the MORE_DATA bit to indicate that no more data exists and to signal that the unscheduled service period has ended. If the reserved buffer has only one frame of data stored in the buffer, it will transmit that data frame, and likewise, it will set the MÁS_DATOS bit to indicate that there is no more data if the added buffer is empty, otherwise, the non-reserved data in the aggregate buffer will also be transmitted to the mobile station. In response to the reception of the response frame, in the preference mode, the mobile station transmits an acknowledgment 520 in a short intermediate frame 518 time period. If the response frame indicated the end of the service period not Currently programmed, the mobile station then places the WLAN sub-system in a low-energy state after receiving the response frame at time 522. Referring now to Figure 6, a flow chart 600 illustrating a method is shown. hybrid to perform the energy-saving operation in a mobile station of a WLAN according to the invention. At the beginning 602 of the method, the mobile station and the access point have negotiated a reserved traffic transmission and the mobile station has placed its WLAN sub-system in the low power mode until a scheduled service period starts. At the start of a scheduled service period, the mobile station starts energizing the WLAN sub-system (604), to start the scheduled negotiation (606). During the scheduled service period, the access point transmits the reserved data to the mobile station, and identifies the transmission of traffic with the unique traffic transmission identifier. At the end of the scheduled service period, the access point may still have data that has not been transmitted to the mobile station, and so indicates it in a last frame transmitted to the mobile station. The access point may indicate the category buffer information by detailed access by describing the access categories of the information stored in the buffer at the access point. In IEEE 802.11, there are currently four access categories described, including the categories of voice, video, and best effort. During the scheduled service period, the mobile station can also transmit the data to the access point. After the scheduled negotiation ends, the mobile station can place the WLAN sub-system back into a low-energy state (608). Subsequently, the mobile station determines whether a negotiation does not program is appropriate or not (610), such as by means of the detailed access category buffer storage information provided by the access point, for example. The mobile station can weigh various parameters, such as the current battery status of the mobile station, the type of current data at the access point, and so on. If the mobile station decides that an unscheduled negotiation is appropriate, the mobile station takes the WLAN sub-system out of the low energy mode to the active mode (612), and initiates an unscheduled negotiation (614) according to the method shown and described in figures 4-5. Once the unscheduled negotiation ends, the mobile station again places the WLAN sub-system in the low power mode (616). Subsequently, the mobile station waits for the next scheduled service period (618) and repeats the procedure. Similarly, the mobile station had determined that an unscheduled negotiation would not be appropriate (610), due, for example, to low battery power or data at the access point are of low priority, the mobile station will skip the unscheduled negotiation and wait for the next scheduled negotiation (618). Referring now to Figure 7, a flow diagram of a frame exchange procedure of the mobile station during an unscheduled negotiation according to the invention is shown. At start 700, the mobile station checks to see if there are data currently pending for the transmission of reserved traffic from voice processors or other media processors in real time. If not, then the mobile station waits for the sequential interrogation window to time a sequential interrogation window. The mobile station also competes for the WLAN channel during this time. Once the channel is acquired, the mobile station transmits a sequential interrogation frame (702). The sequential interrogation frame will contain the data, in case the data were pending, otherwise, the sequential interrogation frame will be a null frame. The sequential interrogation frame identifies the transmission of reserved traffic. Preferably, the reserved traffic transmission is identified by its TSID, and the presence of the traffic transmission identifier indicates to the access point that the mobile station is using an unscheduled negotiation. In an embodiment of the invention, the aggregate response of the access point is the default mode, but the aggregate response mode can also be selected, and it can be indicated that the aggregate response in the sequential interrogation frame is desired. In the preference mode, the access point transmits an acknowledgment that is received by means of the mobile station (703). If acknowledgment (704) is not received, the mobile station may return to wait, then retransmit the sequential interrogation frame. After transmitting the sequential interrogation frame, and, in the preference mode, after receiving 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 to wait before it initiates an error procedure, assuming an access point failure to respond. However, assuming normal operation, the access point will transmit an aggregation of response frames that the mobile station (706) will receive. In the transmission data of the aggregated buffer, the data pertaining to the transmission of traffic identified by the TSID used by the mobile station in the sequential interrogation frame before the non-reserved data in the aggregate response can be transmitted first. Again, in the preference mode, the mobile station will transmit an acknowledgment to ensure that there is a successful supply by the access point. After receiving the response frame, the mobile station checks the EUSP bit to see if the UPSD service period has ended. In the preference mode, the MORE_DATA bit can be used to signal when more data from the access point (708) comes, and when set, it indicates that the service period continues until at least one response frame is received. If the MORE_DATA bit indicates that subsequent frames arrive, then the mobile station remains active to receive them just as it did for the first response frame. It is contemplated that subsequent response frames may contain data for a different reserved traffic transmission, also in use by the mobile station, or for the transmission of current reserved traffic. Once the response frame is received indicating that no more access point data arrives, the procedure ends (710) and the mobile station places the WLAN sub-system in the low power mode. Referring now to Figure 8, there is shown a flow chart 800 of a method of storing data in the buffer for an access point, according to the invention. At the start (802) of the method, the access point has admitted a reserved traffic transmission to establish a call for a mobile station. The data packets of a network for the access point that are designed for the mobile station arrive. As the data packets arrive, the access point checks to see if the data is intended for a mobile station that is currently in an energy saving mode (804). If the mobile station for which an incoming packet is intended is not currently in an energy saving mode, the access point transmits the packet (806) 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 an inherited energy saving mode or the current unscheduled energy saving mode (808). If the mobile station is using an inherited energy saving mode, then the access point stores the packet in an unreserved buffer (810) in the buffer memory and signals that the state of the mobile station's buffer is found. in, for example, a periodic beacon frame transmitted by the access point. If the packet is associated with a supported stream for a mobile station that uses the power saving mode, then the packet is stored in the reserved buffer (812). Therefore, the invention provides a method for performing the energy saving operation in a wireless local area network (WLAN) by means of a mobile station establishing a periodic program of recurring service between the mobile station and an access point . Scheduled service periods occur at periodic intervals and serve to maintain a reserved traffic transmission. The reserved traffic transmission is identified by means of a reserved traffic transmission identifier, and the mobile station has its WLAN subsystem in a low energy mode initially. The method starts by energizing the WLAN sub-system of the mobile station and initiates a scheduled service period. At the end of the scheduled service period, the mobile station receives from the access point an indication that the access point has more data in a buffer of the access point for the mobile station. After receiving the last frame of the scheduled service period, the mobile station places the WLAN sub-system in a low power mode. If the mobile station decides that it is appropriate, then the mobile station begins to initiate an unscheduled service period to retrieve the remaining data stored in the buffer at the access point for the mobile station. The unscheduled service period starts by energizing the WLAN sub-system and transmitting a sequential interrogation frame to the access point. The sequential interrogation frame includes the reserved traffic transmission identifier. In response, the mobile station receives at least one response frame from the access point. At the conclusion of the unscheduled service period, the mobile station places the WLAN sub-system in the low power mode. In a modality that receives the response frame, it includes receiving an aggregate response in which both reserved and non-reserved data are received. The aggregate mode can be a default mode, or it can be triggered by transmitting the sequential interrogation frame with a set of aggregated bits. The current method also prescribes a method for recovering the data of an access point by means of a mobile station in a wireless local area network (WLAN), where the reserved data corresponds to a reserved traffic transmission and is identified by means of of a reserved traffic transmission identifier. The method includes developing a scheduled negotiation between the mobile station and the access point during a scheduled service period. The mobile station transitions from a low power WLAN mode to an active WLAN mode to initiate the scheduled negotiation, and subsequently makes the transition from the active WLAN mode to the low power WLAN mode after completing the scheduled negotiation. After the scheduled negotiation is completed, the mobile station begins to develop an unscheduled negotiation between the mobile station and the access point during an unscheduled service period. The mobile station transitions from a low energy WLAN mode to an active WLAN mode to initiate unscheduled negotiation, and then makes the transition from the active WLAN mode to a low power WLAN mode until the unscheduled negotiation is completed. It is contemplated that the unscheduled negotiation may be developed in response to the access point by indicating at the end of the scheduled service period that the access point still has data for the mobile station, or, alternatively, the mobile station may have data to transmit to the mobile station. access point. If the access point indicates at the end of the scheduled negotiation that there is still data stored in the buffer in the access point, the access point may indicate the type of data, such as the access category of the data and whether the data are or are not part of a reserved traffic transmission. Data that is part of a reserved traffic transmission can be part of a live voice call. The mobile station can decide whether or not to initiate an unscheduled service period by checking various parameters, such as, for example, battery power status, signal quality level, the priority of the data stored in the buffer at the access point, and so on. Since the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (10)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as a priority: CLAIMS

1. - A method to develop the operation of saving energy in a wireless local area network

(WLAN) by means of a mobile station, a recurring service period program established between the mobile station and an access point including regularly scheduled service periods for a reserved traffic transmission, the reserved traffic transmission identified by an identifier reserved traffic transmission, the mobile station having a WLAN sub-system that is initially in a low power mode, the method comprises: energizing the WLAN sub-system of the mobile station; start a scheduled service period; receiving from the access point at the end of a scheduled service period, an indication that the access point has more reserved data from a reserved traffic transmission in a buffer of the access point at the end of the scheduled service period; place the WLAN sub-system in low energy mode at the end of the scheduled service period; initiating an unscheduled service period for recovering the remaining data stored in the buffer at the access point for the mobile station, comprising: energizing the WLAN sub-system; transmitting a sequential interrogation frame to the access point, the sequential interrogation frame including the reserved traffic transmission identifier; receiving at least one response frame from the access point in response to the transmission of the sequential interrogation frame; and placing the WLAN sub-system in low energy mode after receiving at least one response frame. 2. A method for developing the energy saving operation according to claim 1, characterized in that it receives at least one response frame comprising receiving at least one aggregate response frame.

3. A method for developing the energy saving operation according to claim 2, characterized in that it receives the aggregate response frame, which is received in response to the transmission of the sequential interrogation frame, with a set of bits aggregates

4. - A method for developing the energy saving operation according to claim 1, further comprising receiving a recognition frame in the mobile station from the access point in the WLAN channel in response to the transmission of the sequential interrogation frame.

5. A method for developing the energy saving operation according to claim 1, further comprising transmitting a recognition branch from the mobile station to the access point in the WLAN channel in response to the reception of at least one frame of response.

6. A method for developing the energy saving operation according to claim 2, characterized in that receiving at least one aggregate response frame includes receiving a header of a first frame of the aggregate response having a set of bits of MORE_DATA to indicate a second response frame that will be transmitted accordingly; the method further comprises receiving a second response frame in the mobile station.

7. A method for developing the energy saving operation according to claim 1, characterized in that transmitting the sequential interrogation frame comprises transmitting a null frame.

8. - A method for developing the energy saving operation according to claim 1, further comprising acquiring the WLAN channel after activating the WLAN sub-system, developed by contention for the WLAN channel.

9. A method for developing the energy saving operation according to claim 8, characterized in that contention for the WLAN channel is developed by carrier detection.

10. A method for recovering the data from an access point by means of a mobile station in a wireless local area network (WLAN), the reserved data corresponding to a reserved traffic transmission and identified by a traffic transmission identifier reserved, the method comprises: developing a scheduled negotiation between the mobile station and the access point during a scheduled service period, the mobile station makes the transition from a low energy WLAN mode to an active WLAN mode to initiate the scheduled negotiation, and then transition from the active WLAN mode to a low-power WLAN mode until the scheduled negotiation is complete; and developing an unscheduled negotiation between the mobile station and the access point during an unscheduled service period, the mobile station transitions from a low power WLAN mode to an active WLAN mode to initiate unscheduled negotiation, and subsequently performs the transition from the active WLAN mode to a low power WLAN mode until the unscheduled negotiation is completed.