Methods and apparatus for saving power by designating frame interlaces in communication systems

The disclosed embodiments provide for methods and systems for designating at least one frame interlace out of a set of frame interlaces, by identifying a number of frame interlaces, wherein information may be communicated on the identified frame interlaces, and designating the identified frame interlaces to at least one access terminal, such that the access terminal may save power by monitoring only the designated frame interlaces.

BACKGROUND

The present invention relates generally to communications and more specifically to techniques for saving power by efficiently designating a number of frame interlaces in a communication system.

Communication systems are widely deployed to provide various communication services such as voice, packet data, and so on. These systems may be time, frequency, and/or code division multiple-access systems capable of supporting communication with multiple users simultaneously by sharing the available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Multiple-Carrier CDMA (MC-CDMA), Wideband CDMA (W-CDMA), High-Speed Downlink, Packet Access (HSDPA), Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems.

A communication system may employ frame interlaces to communicate information. There is therefore a need in the art for techniques to designate an optimum number of frame interlaces that would improve power consumption.

SUMMARY

The disclosed embodiments provide for methods and systems for designating at least one frame interlace out of a set of frame interlaces, by identifying a first number of frame interlaces, wherein information may be communicated on the identified frame interlaces, and designating the identified frame interlaces to at least one access terminal, such that the access terminal may save power by monitoring only the designated frame interlaces.

The disclosed embodiments also provide for methods and systems for requesting a number of frame interlaces by identifying a number of frame interlaces that an access terminal can monitor, based on at least available power at the access point, and providing the identified number of frame interlaces to an access point:

The disclosed embodiments also provide for methods and systems changing a designated set of frame interlaces from a first number to a second number by receiving a request for changing a designated set of frame interlaces from a first number to a second number, identifying a second number of frame interlaces, and designating the identified second number of frame interlaces to the access point, such that the access terminal may save power by monitoring only the designated second number of frame interlaces.

DETAILED DESCRIPTION

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or design described herein is “exemplary” and is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

An “access terminal” refers to a device providing voice and/or data connectivity to a user. An access terminal may be connected to a computing device such as a laptop computer or desktop computer, or it may be a self contained device such as a personal digital assistant. An access terminal can also be called a subscriber unit, mobile station, mobile, remote station, remote terminal, user terminal user agent, or user equipment. An access terminal may be a subscriber station, wireless device, cellular telephone, PCS telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device having wireless connection capability, or other processing device connected to a wireless modem.

An “access point” refers to a device in an access network that communicates over the air-interface, through one or more sectors, with the access terminals. The access point acts as a router between the access terminal and the rest of the access network, which may comprise an IP network, by converting received air-interface frames to IP packets. Access point also coordinates the management of attributes for the air interface.

In one embodiment, an access terminal and an access point may operate in one of two modes: “selected-interlace-mode-on” or “selected-interlace-mode-off.” In the selected-interlace-mode-on mode, an access point sends certain assignments to an access terminal only on a set of designated frame interlaces called the “selected-interlace -set.” In the selected-interlace-mode-off mode, no restrictions are placed on the frames on which the access point and access terminal may communicate.

In one embodiment, an access point may enter the “selected-interlace-mode-on” mode upon sending a “selected-interlace” message with “enable bit” set to “1,” and an access terminal may enter the “selected-interlace-on-mode” mode upon receiving a “selected-interlace” message with “enable bit” set to “1” The access terminal may enter the “selected-interlace-mode-off” mode upon receiving a “selected -interlace” message with “enable bit” set to “0,” or upon handoff. The access point may enter the “selected-interlace-mode-off” mode upon sending a “selected-interlace” message with “enable bit” set to “0,” or upon handoff. When an access terminal receives a “selected-interlace-off” message with “enable bit” set to “0,” the access terminal may respond with a “selected-interlace-acknowledgement” message.

To change an existing selected-interlace assignment to an access terminal, the access point may first disable the existing “selected-interlace-mode,” and then send a new “selected-interlace” message. Upon entering the “selected-interlace -mode-on” mode, an access terminal and access point may generate “selected-interlace-enabled” indications, and upon entering the “selected-interlace-off” mode, the access terminal and access point may generate “selected-interlace-disabled” indications.

FIG. 1shows one embodiment of frame-interlace allocation for communicating assignments on selected frames. The AP may communicate assignment with an AT on one or more designated frame interlaces. A frame interlace may include a periodic or non-periodic group of frames. For example, frame interlace “0” may include frames {0,6,12, . . . }; frame interlace “1” may include frames {1,7,13, . . . }; frame interlace “2” may include frames {2,8,14, . . . }; and frame interlace “5” may include frames {5,11,17, . . . }. In one embodiment, the AP may employ one or more frame interlaces to communicate information to an AT. For example, after sending frame “0” of frame interlace “0”, if the AP receives an acknowledgement (ACK) from the target AT, the AP sends new information in frame “6.” Otherwise the AP may resend the same information in frame “6.”

In one embodiment, the AP may employ some or all available frame interlaces, as shown inFIG. 1, for communicating assignments. However, an AT needs to read all the frames for possible availability of assignments. In this case, precious power will be wasted at the AT. Therefore, AT power may be saved if the AT and the AP negotiate which frame interlaces are being employed by the AP. For example, if it is negotiated that the AP will send assignments only on frame interlaces “0” and “2”, then AT would only need to monitor or read frames0,2,6,8,12,14, and so on.

In one embodiment, the number and identity of the selected frame interlaces are negotiated between the AP and the AT. For example, the AT may request a first number of frame interlaces that AT may afford to monitor, based on the available power or other considerations. The AT may also request an increase or decrease in the number of frame interlaces already designated by the AP. In response, the AP accommodates the request received from the AT, and informs the AT of a designated second number of selected frame interlaces.

The AP may designate a number of frame interlaces based on several factors. In one embodiment, the access point avoids to designate the same frame interlaces to two or more ATs. In another embodiment, the AP may align a designated frame interlace with the frames that carry power control channel. For example, as shown inFIG. 1, if the power control channel is carried on frame interlace “2,” one of the frame interlaces that the AP designates would be frame interlace “2.” In another embodiment, the AP may align a designated frame interlace with the frames adjacent or as close as possible to the frames that carry power control channel. For example as shown inFIG. 1, if the power control channel is carried on frame interlace “2,” a second one of the frame interlaces that the AP designates would be either frame interlace “1” or frame interlace “3.”

FIG. 2shows one flow diagram for designating frame interlaces. In step202, an AT may send a selected-interlace-request (SIR), to request selected-frame-interlace-mode. The request may include a message ID, an identification of the target AP or a sector to which the request is directed, e.g., PilotPN of the target sector, and/or number of interlaces, which may be based on the available power at the AT. In step204, the AP may send a selected-interlace-designation-message (SIDM) to assign selected-interlace-mode to the AT. The SIDM message may include a message ID, the number of designated interlaces assigned to the AT, an ID assigned to each assigned interlace, and/or an identification of the AP or the sector that sent this message, e.g., PilotPN of the sending sector. In step206, the AT may send a selected interlace acknowledgement (SIA) upon receiving an SIDM message. The SIA message may include a message ID, an identification of the target AP or a sector to which the SIA message is directed, e.g., PilotPN of the target sector, and an indication that the AT has enabled its selected-interlace-mode.

FIG. 3shows a block diagram of a access point110xand an access terminal120x, for implementing interlace allocation and designation as discussed above in connection withFIG. 1andFIG. 2. For the reverse link, at terminal120x, a transmit (TX) data processor314receives traffic data from a data buffer312, processes (e.g., encodes, interleaves, and symbol maps) each data packet based on a selected coding and modulation scheme, and provides data symbols. A data symbol is a modulation symbol for data, and a pilot symbol is a modulation symbol for pilot (which is known a priori). A modulator316receives the data symbols, pilot symbols, and possibly signaling for the reverse link, performs OFDM modulation and/or other processing as specified by the system, and provides a stream of output chips. A transmitter unit (TMTR)318processes (e.g., converts to analog, filters, amplifies, and frequency up converts) the output chip stream and generates a modulated signal, which is transmitted from an antenna320.

At access point10x, the modulated signals transmitted by terminal120xand other terminals in communication with access point10xare received by an antenna352. A receiver unit (RCVR)354processes (e.g., conditions and digitizes) the received signal from antenna352and provides received samples. A demodulator (Demod)356processes (e.g., demodulates and detects) the received samples and provides detected data symbols, which are noisy estimate of the data symbols transmitted by the terminals to access point110x. A receive (RX) data processor358processes (e.g., symbol demaps, deinterleaves, and decodes) the detected data symbols for each terminal and provides decoded data for that terminal.

For the forward link, at access point110x, traffic data is processed by a TX data processor360to generate data symbols. A modulator362receives the data symbols, pilot symbols, and signaling for the forward link, performs OFDM modulation and/or other pertinent processing, and provides an output chip stream, which is further conditioned by a transmitter unit364and transmitted from antenna352. The forward link signaling may comprise power control commands generated by a controller370for all terminals transmitting on the reverse link to base station10x. At terminal120x, the modulated signal transmitted by base station110xis received by antenna320, conditioned and digitized by a receiver unit322, and processed by a demodulator324to obtain detected data symbols. An RX data processor326processes the detected data symbols and provides decoded data for the terminal and the forward link signaling. Controller330receives the power control commands, and controls data transmission and transmits power on the reverse link to access point110x. Controllers330and370direct the operation of terminal120xand access point110x, respectively. Memory units332and372store program codes and data used by controllers330and370, respectively, to implement the frame interlace allocation and designation as discussed above.

FIG. 4shows one embodiment of an access terminal. The processing units in the AT may include a first module402that identifies a number of frame interlaces, e.g., based on at least the available power on the AT, a second module404that requests a number of frame interlaces from an AP, a third module406that receives and processes designated frame interlaces, and a four module408that sends an ACK message to the AP upon receiving the designated frame interlaces.

FIG. 5shows one embodiment of an access point. The processing units in the AP may include a first module502that receives a request from one or more ATs for a number of frame interlaces, a second module504that identifies a number of frame interlaces, a third module506that designates the identified frame interlaces, and a fourth module508that sends the designates frame interlaces to one or more ATs.

FIG. 6shows a flow diagram for an access terminal. In one embodiment, the AT may monitor some factors on the AT, such as the available power, in step602. The AT may also identify, in step604, a number of frame interlaces that the AT may support, e.g., based on the determined available power at the AT. Whether or not the AT performs steps602and604initially, the AT requests a number of frame interlaces, in step606. The AT may receive a number of designated frame interlaces, in step608, optionally send an ACK message upon receiving the designated frame interlaces, in step610, and start monitoring only the designated frame interlaces, in step612, thus saving power.

FIG. 7shows a flow diagram for an access point. In one embodiment, the AP may receive requests for selected frame interlaces, in step702, from at one or more ATs. Whether or not the AP receives a request, the AP identifies and designates a number of frame interlaces, in step704, and sends the designated number of designated frame interlaces to the AT, in step706. The AP may receive, in step708, an ACK message if one has been send by the AT. The AP sends assignments to the target AT only on the designated frame interlaces, in step710.

According to the disclosed embodiments, the AP and the ATs may negotiate on a set of designated frame interlaces that the AP may employ to communicate information, thereby allowing the AT to monitor only the designated frames. Therefore, a target AT would not need to waste limited power to monitor all the frames.

The disclosed embodiments may be applied to any one or combinations of the following technologies: Code Division Multiple Access (CDMA) systems, Multiple-Carrier CDMA (MC-CDMA), Wideband CDMA (W-CDMA), High-Speed Downlink Packet Access (HSDPA), Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems.

The signaling transmission techniques described herein may be implemented by various means. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the processing units used to process (e.g., compress and encode) signaling may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. The processing units used to decode and decompress the signaling may also be implemented with one or more ASICs, DSPs, and so on.

For a software implementation, the signaling transmission techniques may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit (e.g., memory unit332or372inFIG. 3) and executed by a processor (e.g., controller330or370). The memory unit may be implemented within the processor or external to the processor.