HK1140591A

HK1140591A - Adapting transmission and reception on time in packet based cellular systems

Info

Publication number: HK1140591A
Application number: HK10106647.2A
Authority: HK
Inventors: Bengt Lindoff; Jacobus Cornelis Haartsen
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2006-12-27
Filing date: 2007-12-16
Publication date: 2010-10-15

Description

Adapting transmission and reception in time in a packet-based cellular system

Background

The present invention relates to packet-based cellular communication systems, and more particularly to a method and apparatus for reducing the number of receptions and transmissions of a communication device, thereby reducing power consumption in the communication device.

Cellular communication systems are becoming more and more packet oriented (e.g., using the internet protocol- "IP"). For example, the third generation partnership project (3GPP) has extended Wideband Code Division Multiple Access (WCDMA) by High Speed Packet Access (HSPA) which provides transport and control channels optimized for packet services. It is expected that in future systems even typical circuit switched services like voice will be transported over packet based systems (e.g. voice over IP- "VoIP"). This may be evidenced by, for example, Continuous Packet Connectivity (CPC) (release 7 of the 3GPP standard), an evolution of the HSPA standard optimized for low data rate packet services, such as VoIP. As another example, a new Orthogonal Frequency Division Multiplexing (OFDM) based system, Long Term Evolution (LTE), would be a packet-only based system where voice must be transmitted over VoIP.

Having a packet-based structure enables a communication terminal to enter a "sleep" mode between the reception and transmission of packets. The sleep mode typically includes disabling the radio transmitter and/or radio receiver (in discontinuous transmission/discontinuous reception- "DTX/DRX") and one or more other baseband processors for modulation and demodulation of the radio signal. The use of DTX/DRX allows power consumption to be significantly reduced.

In packet-based systems, packets are transmitted in the Downlink (DL) direction as well as the Uplink (UL) direction. In either case, the transmission is considered to be made on a link referred to herein throughout as the "originating link". In modern packet-based systems, the receiver of a packet typically transmits information in the opposite direction (in the link referred to throughout this document as the "response link") that indicates whether the packet was decoded correctly (acknowledgement or "ACK") or incorrectly (negative acknowledgement or "NAK") (ACK/NAK signaling). If a NAK occurs, the packet is retransmitted. Thus, in the DL direction, a base station transceiver (e.g., "node B" in universal mobile telecommunications system- "UMTS") transmits a data packet to a User Equipment (UE), which decodes the packet and transmits an ACK or NAK upward to the base station transceiver. If a NAK is transmitted, the same packet is retransmitted and the UE decodes the packet (either alone in the so-called "automatic repeat request" - "ARQ" system or in combination with a packet received earlier in the so-called "hybrid automatic repeat request" - "HARQ" system). The same procedure is performed in the UL direction, but with the UE acting as the transmitter and the base transceiver station as the receiver.

The protocol and timing of packet transmissions and the exact timing relationship between packet transmissions and their corresponding ACKs/NAKs depend on which specifications are being implemented. For example, in HSPA DL, the ACK/NAK should be transmitted from the UE approximately 5 milliseconds after the DL packet is received, while the ACK/NAK for the UL packet should be transmitted between 6.5-8.5 milliseconds after the UL packet is received. As another example, in some systems (e.g., HSPA UL), the UE may transmit (small) packets without permission from the base station, while in other systems (e.g., LTE), the UE is always required to issue a scheduling request that requests allocation of UL resources for transmitting information.

In a typical system, the utilization of DL is separate from the utilization of UL; i.e. DL packets are received independently of UL packets. This reduces the likelihood of entering DRX/DTX mode (and hence the likelihood of power saving) since the radio needs to be turned on for both transmitting/receiving packets and ACK/NAK control signaling.

Another important aspect of cellular systems is mobility. In order to be able to perform handover, the UE must regularly measure its environment. In HSPA and in LTE, reuse of 1 is allowed, which means that neighboring cells transmit on the same carrier. Thus, the inventors have recognized that it is theoretically possible for a UE to simultaneously receive data and perform DL signal strength measurements (intra-frequency measurements). However, in conventional systems, the measurements for handover are made independently of packet reception and transmission, as this further reduces the likelihood of entering sleep mode, thus reducing the potential power savings that could otherwise be obtained by optimally using DRX/DTX capabilities.

In view of the above general discussion, it is apparent that there is a need for methods and apparatus that more optimally utilize the system potential to reduce power consumption.

Disclosure of Invention

It should be emphasized that the terms "comprises" and "comprising," when used in this specification, are taken to specify the presence of stated features, integers, steps or components but the use of these terms does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

According to one aspect of the present invention, the above and other objects are achieved in methods and devices for operating a first transceiver in a packet-based communication system, wherein the first transceiver comprises a receiver and a transmitter for bi-directional communication with a second transceiver. Such operations include determining an execution time for a first operation of the first transceiver based at least in part on an expected execution time for an unrelated operation of the first transceiver. The determined execution time and the expected execution time are used in causing the first transceiver to bundle (bundling) transceiver operations that are not related to each other. Many alternative embodiments make use of this principle.

In one aspect, operating the first transceiver includes causing the first transceiver to transmit bundled information, wherein the bundled information includes initiating link information and responding link information. For example, the initiating link information may be a data packet (e.g., a voice over IP- "VoIP" packet) and the responding link information may be an ACK/NAK.

In another aspect, operating the first transceiver includes operating a receiver to receive a first signal from the second transceiver over the initiation link. After confirming that the information carried by the first signal requires the return link information to be sent to the second transceiver, a time period is determined during which the first transceiver can begin bundled transmission of the return link information and the originating link information that is not related to the information carried by the first signal. Then, within a determined time period, bundled transmission of the initiation link information and the return link information is started.

In such embodiments, initiation link information unrelated to information carried by the first signal may be made available to the first transceiver prior to operating the receiver to receive the first signal from the second transceiver. To address such situations, in some embodiments determining a period of time during which the first transceiver may begin bundled transmission of the initiating link information and the responding link information comprises detecting availability of initiating link information that is unrelated to information carried by the first signal; and adding the predetermined response delay time to the time of arrival of the information carried by the first signal. For example, the information carried by the first signal may be a first VoIP packet; the response link information may be ACK/NACK, which indicates whether the second transceiver should retransmit the first VoIP packet; and the initiating link information that is not related to the information carried by the first signal may be a second VoIP packet. In another example, the information carried by the first signal may be a scheduling request; the response link information may be resource allocation information; and the originating link information that is not related to the information carried by the first signal may be a VoIP packet.

In another aspect, operating the first transceiver may include causing the first transceiver to receive bundled information, wherein the bundled information includes initiating link information and responding link information. For example, the initiating link information may be carried on a signal indicative of the radio environment of the first transceiver (e.g., for handover measurements); and the response link information may be ACK/NAK.

In yet another aspect, operating the first transceiver may include operating a transmitter to transmit an initiating link information signal to the second transceiver. A time period is determined during which the first transceiver will expect to receive a response to the initiating link information signal. In response to detecting that the first transceiver should perform one or more measurements of the radio environment of the first transceiver, the first transceiver performs bundled receiver operations for a period of time during which the first transceiver will expect to receive a response to the initiating link information, the bundled receiver operations including receiving the response to the initiating link information signal and a signal indicative of the radio environment of the first transceiver.

In yet another aspect, the operation of the first transceiver may include determining a time at which the first transceiver will expect to receive a first signal on the initiation link. After detecting that information destined for the second transceiver is available for transmission, logic in the first transceiver determines an earlier time at which the first transceiver will begin transmitting a second signal carrying information destined for the second transceiver by subtracting a predetermined response delay time from a time at which the first transceiver will expect to receive the first signal. Then, at this earlier time, the second signal is transmitted to the second transceiver. Thereafter, for a time period that includes a time at which the first transceiver will expect to receive the first signal, bundled receiver operations are performed that include receiving the first signal on an initiating link and receiving a response to the second signal on a responding link.

In yet another aspect, the first transceiver operation may include transmitting initiation link information to the second transceiver and receiving unrelated initiation link information from the second transceiver. Such operation allows the transceiver to be able to combine the transmitter and receiver operations within the same time window.

In one such embodiment, the first transceiver operation includes receiving a scheduling request from the second transceiver. In response to the received scheduling request, resource allocation information is determined, which includes an indicator of a future time instant at which the second transceiver should start transmitting the first signal carrying initiation link information to the first transceiver, wherein the determining of the resource allocation information is based at least in part on when the first transceiver will be able to transmit the second signal carrying initiation link information to the second transceiver. The transmitter is then operated to transmit the second signal while the receiver is operated to receive the first signal substantially simultaneously for a period of time that includes the future time.

In some alternatives, determining the resource allocation information comprises detecting whether originating link information to be carried by the second signal is available, and if the originating link information to be carried by the second signal is not available, waiting for the originating link information to be carried by the second signal to become available before determining an indicator of a future time instant at which the second transceiver should begin transmitting the first signal carrying the originating link information to the first transceiver.

Other aspects include operating the receiver to listen for scheduling requests only at predetermined times; and/or operate the transmitter to transmit the resource allocation information to the second transceiver only at predetermined times.

Drawings

The objects and advantages of the present invention will be understood by reading the following detailed description in conjunction with the drawings, in which:

fig. 1 is a flow chart of steps/procedures performed by components of a UE in an exemplary embodiment.

Fig. 2 is a flow diagram of steps/processes performed by components of a UE engaged in VoIP communication in an alternative exemplary embodiment.

Figure 3 is a flow chart of steps/processes performed by components of a UE engaged in VoIP communication in yet another alternative exemplary embodiment.

Fig. 4 is a block diagram of an exemplary UE adapted to implement various aspects of the present invention.

Fig. 5 is a flow diagram of steps/processes performed by components of a node B engaged in VoIP communications in an exemplary embodiment.

Figure 6 is a flow chart of steps/processes performed by components of a node B engaged in VoIP communication in an alternative exemplary embodiment.

Fig. 7a and 7b illustrate relative timing of various operations according to the exemplary embodiment of fig. 6.

Detailed Description

Various features of the present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like parts throughout.

Various aspects of the invention will now be described in more detail in connection with a number of exemplary embodiments. To facilitate an understanding of the invention, many aspects of the invention are described in terms of sequences of actions to be performed by elements of a computer system or other hardware capable of executing programmed instructions. It will be recognized that in each of the embodiments, the various actions could be performed by specialized circuits (e.g., discrete logic gates interconnected to perform a specialized function), by program instructions being executed by one or more processors, or by a combination of both. Moreover, the invention can also be considered to be embodied entirely within any form of computer readable carrier, such as solid-state memory, magnetic disk, optical disk or carrier wave (such as radio frequency, audio frequency or optical frequency carrier waves, etc.) containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein. Thus, the various aspects of the invention may be embodied in a number of different forms, and all such forms are contemplated to be within the scope of the invention. For each of the various aspects of the invention, any such form of embodiments may be referred to herein as "logic configured to" perform a described action, or alternatively as "logic that" performs a described action.

Broadly contemplated aspects of embodiments consistent with the present invention include combining even unrelated information items into a single bundle or combining them into a single transmitter and/or receiver operation. This not only enables the transceiver to take advantage of as much of its information transfer capabilities as possible, but also creates longer periods of transceiver inactivity (stretch) during which the transceiver can operate in a low power saving manner.

"binding" can be accomplished in a number of ways. For example, different information may be transmitted simultaneously (e.g., in parallel or simultaneously) by using different spreading codes (e.g., in WCDMA or other code division multiple access systems). Simultaneous transmissions may be all (i.e., multiple transmissions all start and end at the same respective time as each other) or partial, i.e., overlapping for some period of time, such as when one transmission takes longer than another, or when another transmission starting earlier from one transmission continues, or a combination of these. Alternatively, unrelated information items may be combined in the same packet, which reduces overhead (e.g. only a single header, only one setting cycle (setting period) of power up of e.g. an amplifier, a voltage controlled oscillator, a crystal, etc.). Bundling can even be achieved by: the transceiver operation is combined to allow transmission and reception to occur simultaneously, or one after the other, for example in a half-duplex or TDD system, to enable the circuitry shared between the transmitter and receiver to remain powered up for that duration, thereby eliminating the tuning time of this circuitry. As used herein, the term "bundled" is defined to include each of these possibilities.

In one aspect, various embodiments of the present invention reduce the amount of time to utilize a transceiver of a UE (and thus increase the DTX/DRX cycle of the UE) by bundling events that would otherwise be independently scheduled transmission and reception events, such that, for example, the bundled transmitter and/or receiver operation delivers the initiating link information along with the responding link information in a single transmission and/or reception instance (instance).

In one embodiment, the UE initiated link packet transmission/reception time is adapted to coincide with the time instant when it is known that (uncorrelated) response link information should be transmitted/received. For example, in HSPA systems, each UE is designed to transmit an ACK/NAK (response link information) 5 milliseconds after receiving the initiating link information on the DL. The UE may thus reduce the amount of time its transceiver is turned on by scheduling a UL packet (initiating link information) to be transmitted simultaneously with an ACK/NAK (responding link information).

As another example, applicable to HSPA systems, each UE is designed to expect to receive an ACK/NAK (response link information) 6.5-8.5 milliseconds after having transmitted a UL packet. Because it is known that the receiver of the UE will be on at this time, the UE can reduce the amount of time its receiver is on by scheduling handover measurements to be simultaneous. In this context, the measured signal is not responsive to anything transmitted by the UE and can therefore be considered to be on the initiating link.

This technique of scheduling independent operations with the same transceiver operation (i.e., reception or transmission) to be bundled into a single transceiver activation instance is suitable for delay-sensitive packet services such as VoIP, where packets are generated at regular intervals (e.g., voice packets are output from a vocoder every 20 milliseconds), and where low delay is required (e.g., in VoIP, the maximum acceptable delay is 60 milliseconds, meaning that 3 packets can be transmitted every 60 milliseconds instead of 1 packet every 20 milliseconds). For such services, the UE may buffer an amount of data and transmit the data concurrently with an ACK/NAK response associated with the data received from the node B (which will be received periodically within a known time window, e.g., at least once every 60 milliseconds).

These techniques therefore allow the UE to substantially reduce the amount of time to turn its transceiver on, thereby substantially increasing the DTX/DRX cycle. This in turn contributes to a significant reduction in UE power consumption. These and other aspects will now be described in more detail below.

It is believed that the use of specific examples will be helpful in understanding various aspects of the present invention, and for this reason HSPA scenarios with VoIP services are used herein as an initial example. Thereafter, examples are used herein for illustrative purposes that include the LTE case with VoIP. However, aspects of the present invention are not limited to these particular situations, or to these particular types of communication systems.

As mentioned earlier, in VoIP, a speech encoder generates speech packets once every 20 milliseconds. An IP header is appended to the packet and the resulting VoIP packet (initiating link information) is transmitted to the intended recipient (UE or node B, depending on which entity is transmitting). To optimize capacity in the network, the node B scheduler may decide to connect (connect) or split multiple VoIP packets and thereby transmit the data packets to the UE in a more flexible manner. However, delays above 60 milliseconds are undesirable due to quality constraints. Thus, as can be seen from the above, once VoIP is initiated and running, the UE may expect to receive VoIP packets from the node B at least once every 60 milliseconds.

The same is true in the UL direction. The UE may transmit one or more VoIP packets (originating link information) to the node B at an interval of up to about 60 milliseconds.

Also, in HSPA systems, the UE is allowed to transmit data whenever it wants to transmit, as long as its transmit power (on the enhanced absolute grant channel- "E-AGCH" and/or the enhanced relative grant channel- "E-RGCH") remains below a certain level specified by the level information transmitted from the node B.

This scheduling freedom makes it possible for the UE to adapt its transmission time in order to substantially reduce the on-time of the transmitter (i.e., the time for which the transmitter is activated at a power level sufficient for it to perform its transmit operations). This aspect of the invention will now be described with reference to fig. 1, which is a flow chart of steps/processes performed by components of a UE engaged in VoIP communications in an exemplary embodiment. VoIP packets to be transmitted to the node B are provided by a speech encoder in the UE (step 101). The UE knows approximately when it can expect to receive the next packet from the node B. Therefore, it does not transmit its own packet at this time, but stores its packet in the transmission buffer (step 103).

At the appropriate time, the UE turns on its receiver (step 105) and receives the expected DL packet (initiating link information) (step 107). The receiver is then turned off (step 109) and the received packet is processed in a conventional manner, e.g. including decoding (step 111).

When it is time to transmit an ACK/NAK (response link information) (e.g., 5 milliseconds after receiving the packet on the DL), the UE turns on its transmitter (step 113) and transmits bundled information containing the ACK/NAK response (response link information because it responds to the received DL packet) and the UL VoIP packet (originating link information) stored in the transmit buffer (step 115). This bundling is possible in HSPA because the ACK/NAK is transmitted on a high speed dedicated physical control channel (HS-DPCCH), i.e. using a given channelization code, while the VoIP packet is transmitted on a different channel, i.e. it uses a different channelization code, i.e. an enhanced dedicated physical data channel (E-DPDCH).

After transmission of the ACK/NAK and buffered UL VoIP packets, the transmitter is turned off (step 117) (i.e., its power is reduced to a level insufficient to support transmitter operation). The UE then waits until it is time to expect to receive the ACK/NAK associated with the just transmitted VoIP packet, at which point it turns on its receiver (step 119), receives the ACK/NAK (step 121), and turns off the receiver (step 123). Decodes the received ACK/NAK (step 123) and performs subsequent steps (not shown) in response to whether an ACK or NAK is received.

In another aspect, the node B may follow a similar process that times the transmission of DL packets to coincide with the transmission of ACK/NAKs. When performing this procedure, the UE receives not only ACK/NAK (response link information) but also a dl (voip) packet (origination link information) (not shown) in step 121. The processing of step 123 then includes not only ACK/NAK decoding, but also (VoIP) packet decoding (not shown).

As mentioned earlier, the scheduling freedom makes it possible for the UE to adapt its individual reception times in order to substantially reduce the on-time of the receiver. This aspect of the invention will now be described with reference to fig. 2, which is a flowchart of the steps/processes performed by the components of a UE engaged in VoIP communications in an exemplary embodiment. The present example begins at the point in time when the UE activates its transmitter to transmit bundled information including an ACK/NAK (in response to link information, not shown because it responds to an earlier received packet) and a VoIP packet (initiating link information) stored in a transmission buffer (step 201, equivalent to step 115 described above). In an alternative embodiment, the transmission of the VoIP packet is performed without bundling it with ACK/NAK (not shown). After this transmission, the transmitter is turned off (step 203, equivalent to step 117 described above).

Upon transmitting the VoIP packet, the UE is now in a position where it is expected to receive ACK/NAK (response link information) from the node B, which requires turning on the receiver of the UE. Thus, in aspects of the present embodiment, the UE determines whether scheduling efficiency can be achieved by checking with, for example, its control unit (e.g., a timer with network initialization) to confirm whether it is time to perform handover measurements (or more generally, any measurements of the UE's radio environment) (decision block 205). Typically, the UE needs to perform handover measurements approximately once every 50-70 milliseconds. The duration of each handover measurement is about 10 milliseconds.

If it is not time to perform handover measurements ("no" path out of decision block 205), then ACK/NAK reception processing is performed (step 207). The ACK/NAK reception process is the same as described above corresponding to steps 119, 121, 123, and 125, which makes a repeated description herein unnecessary.

However, if it is at or near the time that the handover measurement is performed ("yes" path out of decision block 205), the UE waits until it is time that the ACK/NAK associated with the VoIP packet just transmitted is expected to be received, and then turns on its receiver (step 209). With the receiver on, the UE bundles the reception of ACK/NAK (response link information) with the execution of handover measurements (step 211), which includes receiving signals from other transmitters (originating link information) that indicate the radio environment of the UE. When both tasks have been completed, the UE turns off the receiver (step 213). The received ACK/NAK is decoded and the handover measurements are analyzed using techniques well known in the art (step 215). The subsequent steps are performed in response to whether an ACK or NAK is received and also based on whether a handover should be performed. These aspects are beyond the scope of the present invention and therefore are not shown here.

It will be appreciated that handover measurements may typically take longer to perform than the amount of time required to receive the ACK/NAK. Thus, handover measurements may be expected to overlap with the reception of ACK/NAKs. According to aspects of embodiments consistent with the invention, the UE times the handover measurement to start at a time that will be certain to have some overlap with the reception of the ACK/NAK, even though this means that the previously scheduled start time for the handover measurement will be adjusted by an acceptable amount of time, or advanced or delayed scheduling.

Another exemplary embodiment will now be described, which illustrates an aspect of the invention, wherein the UE adapts its operation in the following way: the separate receive operations are combined such that those receive operations occur as part of the same receive active instance (i.e., the period of time that the power level provided to the receiver is sufficient to enable it to perform the receive operation). This aspect of the invention will now be described with reference to fig. 3, which is a flow chart of steps/processes performed by components of a UE engaged in VoIP communications in this exemplary embodiment.

In this embodiment, the UE has information that enables it to acknowledge a future point in time or time t at which it expects to receive a data packet (initiating link information) from the node B (step 301). The UE then determines whether it has any packets (initiating link information) in the transmission buffer ready for transmission (decision block 303). If not ("no" path out of decision block 303), it receives and processes the expected data packet at time t in a conventional manner.

However, if there is a packet in the transmit buffer ("yes" path out of decision block 303), the UE adapts its transmission time for the packet such that it will start at time t- τ, where τ is a predefined response delay time (i.e., the expected delay between when the UE transmits the packet and when it can expect to receive an associated ACK/NAK from the node B). In this HSPA example, τ is in the range of 6.5-8.5 milliseconds, the exact number depending on the UL/DL timing information received from higher layer signaling located in the node B. Thus, the packet retrieved by the UE from the transmission buffer is transmitted to the node B at time t- τ (step 307). For any given embodiment, the particular value of τ is not limited to the exemplary range of values indicated above, but rather depends on the timing associated with the particular system in which the UE is designed to operate.

By scheduling the transmission of data packets in this manner, the UE now expects to receive bundled information in one receiver activation instance, which includes the earlier-mentioned expected data packet (initiating link information) and the ACK/NAK (responding link information) associated with the packet just transmitted. Thus, the UE turns on its receiver just before time t (step 309). The UE then receives the expected data packet and the ACK/NAK (step 311). When both have been received, the UE turns off its receiver (step 313) and then decodes the ACK/NAK and processes the received data packet in a known manner (step 315).

To illustrate various aspects of the present invention, the above examples include VoIP packets. However, there is no need to include VoIP packets at all. Rather, aspects of the present invention are also applicable to the transmission and reception of other types of information, such as scheduling requests, handover commands, and other control information. Accordingly, various embodiments of the present invention are not limited to including VoIP packets.

Fig. 4 is a block diagram of an exemplary UE400 adapted to implement various aspects of the present invention. UE400 includes a front end receiver (FE RX)401 for receiving and downconverting data packets. The front-end receiver 401 supplies the baseband signal to the detector 403, and the detector 403 demodulates the received signal. The data generated by the detector 403 is then provided to other components for further processing (not shown).

UE400 also includes a front end transmitter (FE TX) 405. Data to be transmitted is stored in the transmission buffer 407, and the transmission buffer 407 is controlled by the control unit 409. The control unit 409 uses the receiver packet timing information and information about the UL/DL ACK/NAK timing relationship to decide the optimal transmission time in the following sense: preferably, as much information as possible will be bundled for transmission during the same transmitter active instance (e.g., UL VoIP packets, ACK/NAK responses to received DL packets, and UL scheduling requests for upcoming UL packets).

When the control unit 409 determines that transmission should take place, the front-end transmitter 405 is turned on and data is fed from the transmission buffer 407 to the modulator 411. The modulated baseband signal is then fed to a front-end transmitter 405, and the front-end transmitter 405 up-converts the modulated baseband signal to the transmitter's carrier frequency. The generated radio signal is then transmitted to the node B through the antenna 413. When the transmission ends, the front end transmitter 405 is turned off.

The control unit 409 also controls the operation of the front-end receiver 401 and schedules various operations (e.g., as described earlier) with the aim of increasing (and preferably maximizing) the number of information items that can be received in a single receiver activation instance, thereby minimizing the amount of time that the front-end receiver 401 is turned on and maximizing the amount of uninterrupted receiver "off-time".

To this end, the description herein focuses on these techniques: when applied to the operation of a UE, the UE is enabled to adapt the reception and transmission of packets and other information in a packet-based cellular system to enable a substantial reduction in the number of times the transmitter and receiver of the UE are turned on. However, the present invention is by no means limited to application only in UEs. Rather, the basic techniques described above are equally applicable to other transceiver devices, such as node bs (or equivalents) of a cellular communication system. For example, consider the case of an OFDM LTE system. In LTE, the UE is required to send a UL scheduling request (initiating link information) before the UE can transmit packets. In response to the scheduling request, the node B sends DL resource allocation information (in response to link information) to the UE to identify when (in time) and where (in frequency) the UE can send UL packets (e.g., VoIP packets). As will now be described with reference to fig. 5, which is a flow chart of steps/processes performed by components of a node B transceiver participating in VoIP communications in an exemplary embodiment, this arrangement allows for advantageous scheduling adaptation to be performed.

The example begins at a point in time when a DL packet (initiating link information), e.g., a VoIP packet, is made available at the node B for DL transmission to a UE (step 501). Instead of transmitting the DL packet at the first available time, the node B stores the DL packet in a transmission buffer (step 503) and waits until it has received a UL scheduling request (initiating link information) from the UE (step 505). In theory, the node B need not be concerned about breaking down the downlink quality requirement by waiting too long to receive the UL scheduling request, since it knows that the request should be issued within an acceptable predefined time period. In practice, however, it is preferable to include timeout logic (not shown) that ensures that DL packets will not be transmitted later than the last possible time (as determined by quality requirements), even if no UL scheduling request is received (e.g., due to an error in the UL).

Upon receiving the UL request (initiating link information), the node B determines resource allocation information (responding link information) in response to the UL request of the UE (step 507). The node B then turns on its transmitter (step 509) and then transmits bundled information including resource allocation information (response link information) and DL packets (origination link information) already stored in the transmission buffer (step 511). After this transmission, the transmitter of the node B may be turned off (step 513). In practice, whether the transmitter is turned off will depend on whether the eNode B is scheduled to transmit to another UE in the system, which will require keeping the transmitter of the eNode B on. However, it will be appreciated that even if the eNode B keeps its transmitter on after completion of step 513, the UE benefits from this scheduling strategy because it (UE) can bundle its multiple reception instances into a single instance, allowing the UE's transceiver to be turned off at other times.

In addition to achieving power saving in the node B by simultaneously transmitting resource allocation information and DL packets, the UE also benefits from the following: its receiver does not need to be open at scattered times to receive this information. Also, the node B may facilitate further energy saving by determining the resource allocation information in the following manner: the uplink packet transmission (initiating link information) and the ACK/NAK (responding link information) associated with the DL packet for the UE are time aligned so that the UE can bundle those two information for transmission during the same transmission instance, thereby reducing the "transmitter on" time for the UE and the "receiver on" time for the node B.

Still further power savings may be realized by applying the techniques described above to adapt the transmission and reception times of various other information units to achieve bundling. To better appreciate these savings, it is contemplated that in a packet-based system, data bursts may be sent over the channel at generally any time. Having the possibility of transmitting a burst at any time is detrimental to low power operation as the terminal has to listen to the channel continuously. This explains the high power consumption in fully packet-based systems like WLAN802.11 (WiFi). In the currently specified 3GPP LTE system, all data exchange on the enhanced node B ("eNode B") control channel, so there is an opportunity to achieve efficiency.

Continuing with the LTE example, the allocation of resources to different terminals (both in the uplink and downlink directions) is performed by a scheduler located in the eNode B. The scheduler may allocate resource blocks (each defined as a frequency and time block) for downlink transmissions directly by informing the UEs of the allocation on the DL shared control channel. For uplink resource allocation, as mentioned before, the UE first has to send a scheduling request before being able to send data. Upon receiving the scheduling request, the scheduler within the eNode B will respond by generating and transmitting UL resource allocation information to the UE, which informs the UE when, where, and for how long it (UE) can use UL resources.

The behavior of the scheduler is a crucial contribution to the final performance characteristics of the terminal, not only in terms of throughput but also in terms of power consumption. To reduce power consumption when the UE is engaged in low rate packet communications (e.g., for VoIP users), a low power mode should be implemented. These low power modes preferably concentrate all uplink and downlink transactions within a short time window in order to enable the terminal (UE) to sleep most of the time rather than continuously listening to the channel. To achieve this, it is preferable to define a specific point in time at which a specific transaction can be conducted. These predefined specific points in time should be known to both the UE and the eNode B. The UE will then only need to "wake up" (wake up) at and around these specific points in time. For low rate data service users (e.g., VoIP users), the scheduler should attempt to schedule all uplink and downlink transactions as soon as possible to occur within a single time window. Again taking VoIP as an example, it is known that VoIP packets arrive every 20 milliseconds on average. This means that uplink and downlink VoIP packets will arrive within a 20 ms time window, although the exact time of their arrival is not known exactly. (this is in contrast to circuit-switched voice call behavior.) this behavior may be advantageously used as will now be described in connection with the exemplary embodiments below.

Fig. 6 is a flowchart of steps/processes performed by components of an eNode B (or equivalent) engaged in VoIP communications in an alternative exemplary embodiment. The eNode B determines whether a DL packet (initiating link information) is available for transmission (decision block 601) or has received a UL request (initiating link information) from the UE (decision block 603). If neither exists ("no" path out of each of decision blocks 601 and 603), the eNode B continues to wait for either to occur. (for purposes of example, checking for available DL packets is shown as occurring before checking for UL requests, but of course in some architectures the specific order of these steps may be reversed or even performed simultaneously, as this is not an essential feature of the invention.)

If a DL packet is available for transmission ("yes" path out of decision block 601), the packet is stored in the eNode B's transmit buffer (step 605), and the eNode B waits until it receives a UL allocation request from the UE (step 607). Upon receiving the UL allocation request, the scheduler in the eNode B determines resource allocation information that provides for bundling the transmission of DL packets and the reception of UL packets at some future time window beginning at time t (step 609). The eNode B then turns on its transmitter (step 611), transmits the resource allocation information to the UE (step 613), and turns off its transmitter (step 615).

The eNode B then waits until just before time t (step 617), at which point it turns on its transmitter and receiver (step 617) and bundles its DL packets for transmission to the UE with the UL packets received from the UE (step 621). Both the transmitter and receiver may then be turned off (step 623), allowing the eNode B to enter a sleep/low power mode until the next transmission and/or reception is needed. In practice, whether the transmitter is turned off will depend on whether the eNode B is scheduled to transmit packets to another UE in the system. However, it will be appreciated that even if the eNode B keeps its transmitter on after completion of step 621, the UE benefits from this scheduling policy because it (UE) can combine its multiple transmission and reception times into a single time window, allowing the transceiver to be turned off at other times.

Returning to decision block 603, it is possible for the eNode B to receive a UL allocation request from the UE before making the DL packets available (the "yes" path out of decision block 603). In this case, the eNode B waits until a DL packet becomes available for transmission (step 625). When a DL packet is available, the scheduler in the eNode B determines resource allocation information that provides for bundling the transmission of the DL packet and the reception of the UL packet during a certain future time window starting at time t (step 627). Since the eNode B must wait for a DL packet to become available after receiving an uplink allocation request of the UE, the eNode B cannot assume that the UE is in "wake up" and is listening to resource allocation information. Instead, the eNode B waits until the next known wake up time for the UE (step 629), at which point it can proceed to step 611 and operate as described earlier.

Fig. 7a and 7b illustrate the relative timing of various actions according to the exemplary embodiment of fig. 6. In each of these examples, four instances of wake-up time, 5 milliseconds apart from each other, start at predefined times within each 20 millisecond interval. Each wakeup time instance is an allowed time window (wakeup time instance 701) within which to engage in communications (e.g., VoIP). Transactions initiated at one of these predetermined wake-up time instances (e.g., by the UE issuing a scheduling request) are scheduled to complete at a later time, although not otherwise allowed to be initiated, and are not limited to the predetermined wake-up time instances. The UE wakes up at each of these predetermined wake-up time instances for a short period of time (e.g., at most one TTI) to listen to the shared control channel. If the UE is not addressed by another element on the control channel, it will go to sleep for an additional 5 milliseconds until the next wakeup time instance occurs and the process repeats.

Looking first at the example of FIG. 7a, there is shown at time t₁The VoIP packet is made available in the eNodeB. Instead of forwarding this packet immediately to the UE, the eNode B waits until it receives a UL scheduling request from the UE requesting resources for the UE to send its VoIP packets in the uplink. The scheduling request may also request (e.g., using HARQ) that additional resource blocks be reserved for the retransmission. At a certain point in time t₂VoIP packets are made available within the UE. At the next occurring predetermined wake-up time instance t₃Here, the UE transmits its UL scheduling request to the eNode B. The eNode B can then immediately at time t₄Responds with resource allocation information. The resource allocation indicates a future time t₅At which point the exercise will be in the bindingPackets are exchanged on the fly. Therefore, both the eNode B and the UE wait until time t₅Transmitting its packet to the counterpart at this point of time; i.e., substantially simultaneously transmitting/receiving UL and DL packets. As used herein, the term "substantially simultaneous" includes fully simultaneous/parallel operation, at least partially simultaneous/parallel operation, and sufficiently close in time in environments such as half-duplex and TDD to achieve a reduction in overhead due to, for example, eliminating the additional tuning time required to operate circuits shared between the transmitter and receiver.

Any retransmission that needs to be performed is performed immediately after (at time t)₆) Thereafter, the eNode B and the UE re-enter the sleep mode.

It can be seen that in the example of FIG. 7a, t₂＞t₁. Thus, DL VoIP packets are already available and waiting in the eNode B, so that when an uplink scheduling request arrives, the scheduler of the eNode B can immediately schedule UL and DL transmissions.

Fig. 7B illustrates a different example in which the eNode B receives an uplink scheduling request before making DL packets of the eNode B available so that the eNode B cannot immediately schedule any transactions. Specifically, in this example, at time t₁UL VoIP packets are made available in the UE. The UE cannot act on this immediately, but must wait until the next occurring predefined wakeup time instance, at time t₂It sends its uplink scheduling request to the eNode B.

As mentioned before, the eNode B cannot respond to the uplink scheduling request immediately since it has not yet any packets to transmit on the downlink. Some time later, at time t₃DL VoIP packets are made available in the eNode B. The scheduler of the eNode B can now determine the appropriate time to be able to exchange UL and DL VoIP packets in bundled operation, but must wait until the next occurring predefined wake-up time instance t₄The resource allocation information is delivered to the UE. At the scheduled time t₅Operation of eNode B and UE in bundlingExchange their respective packets, then at time t₆Any necessary retransmissions are made. Both the eNodeB and the UE may then enter sleep mode again.

In practice it is advantageous to add a time-out logic (not shown) which will prevent packets in one direction from being lost and directly degrade the quality of service in the other direction. For example, in the example of fig. 7a, the eNode B keeps its available DL packets in a buffer until it receives a scheduling request from the UE. Performing this behavior, it is expected that the scheduling request should be received within a time period sufficient for the eNode B to be able to meet its downlink service requirements. However, if the UE's uplink scheduling request is to become lost in transmission, the eNode B may end holding its DL packets beyond the last allowed time of transmitting its DL packets. Thus, a timer (not shown) can be employed that will cause the eNode B to transmit its DL packets no later than the last possible acceptable time, even if no uplink scheduling request is received.

Similarly, in the example of fig. 7B, a timer can be employed to ensure that the eNode B responds to the UE's uplink scheduling request within a reasonable time even if no DL packets are available to the eNode B due to some error.

The invention has been described with reference to specific embodiments. It will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the embodiments described above. The described embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is given by the appended claims, rather than the preceding description, and all variations and equivalents which fall within the range of the claims are intended to be embraced therein.

Claims

1. A method of operating a first transceiver in a packet-based communication system, wherein the first transceiver comprises a receiver and a transmitter for bi-directional communication with a second transceiver, the method comprising:

determining a time to perform a first operation of the first transceiver based at least in part on an expected time to perform an unrelated operation of the first transceiver; and

using the determined execution time and the expected execution time in a process for the first transceiver to bundle transceiver operations that are not related to each other.

2. The method of claim 1, wherein the process of causing the first transceiver to bundle transceiver operations that are unrelated to each other comprises:

cause the first transceiver to transmit bundled information, wherein the bundled information includes initiating link information and responding link information.

3. The method of claim 2, wherein the initiating link information is a data packet and the responding link information is an ACK/NAK.

4. The method of claim 3, wherein the data packet is a voice over IP (VoIP) packet.

5. The method of claim 1, wherein,

determining the execution time for the first operation of the first transceiver based at least in part on the expected execution time for the unrelated operation of the first transceiver comprises:

operating the receiver to receive a first signal from the second transceiver on an initiation link;

confirming that information carried by the first signal requires sending return link information to the second transceiver; and

determining a time period during which the first transceiver can begin bundled transmission of the return link information and initiation link information that is not related to information carried by the first signal; and

the process of causing the first transceiver to bundle transceiver operations that are unrelated to each other includes:

starting the bundled transmission of the initiating link information and the return link information within the determined time period.

6. The method of claim 5, wherein:

prior to operating the receiver to receive the first signal from the second transceiver, making the initiating link information available to the first transceiver that is not related to information carried by the first signal; and

determining a time period during which the first transceiver may begin the bundled transmission of the initiating link information and the responding link information comprises:

detecting availability of the initiating link information that is not related to information carried by the first signal; and

adding a predetermined response delay time to an arrival time of information carried by the first signal.

7. The method of claim 6, wherein:

the information carried by the first signal is a first VoIP packet;

the response link information is ACK/NACK indicating whether the second transceiver should retransmit the first VoIP packet; and

the initiating link information that is not related to the information carried by the first signal is a second VoIP packet.

8. The method of claim 5, comprising:

determining a time period during which the first transceiver will expect to receive a response to the initiating link information signal;

detecting that the first transceiver should perform one or more measurements of the radio environment of the first transceiver; and

in response to detecting that the first transceiver should perform one or more measurements of the radio environment of the first transceiver, performing the steps of:

performing bundled receiver operations including receiving a response to the initiating link information signal and a signal indicative of a radio environment of the first transceiver during a time period in which the first transceiver will expect to receive a response to the second signal.

9. The method of claim 5, wherein:

the information carried by the first signal is a scheduling request; and

the response link information is resource allocation information.

10. The method of claim 9, wherein the initiating link information that is not related to the information carried by the first signal is a VoIP packet.

11. The method of claim 9, comprising:

detecting that the initiating link information not related to information carried by the first signal is not yet available when the first signal is received from the second transceiver, and thus waiting for information not related to information carried by the first signal to become available before determining a period of time during which the first transceiver can begin the bundled transmission of the responding link information and the initiating link information not related to information carried by the first signal.

12. The method of claim 1, wherein the process of causing the first transceiver to bundle transceiver operations that are unrelated to each other comprises:

causing the first transceiver to receive bundled information, wherein the bundled information includes initiating link information and responding link information.

13. The method of claim 12, wherein:

carrying the initiating link information on a signal indicative of a radio environment of the first transceiver; and

the response link information is an ACK/NAK.

14. The method of claim 1, wherein:

operating the transmitter to transmit an initiate link information signal to the second transceiver;

determining a time period during which the first transceiver will expect to receive a response to the initiating link information signal; and

performing bundled receiver operations including receiving a response to the initiating link information signal and a signal indicative of a radio environment of the first transceiver during a time period in which the first transceiver will expect to receive a response to the initiating link information signal.

15. The method of claim 1, wherein:

determining a time at which the first transceiver will expect to receive a first signal on an initiating link;

detecting that information destined for the second transceiver is available for transmission; and

determining an earlier time instant at which the first transceiver will begin transmitting a second signal carrying information destined for the second transceiver by subtracting a predetermined response delay time from the time instant at which the first transceiver will expect to receive the first signal; and

transmitting the second signal to the second transceiver at the earlier time instant; and

performing bundled receiver operations including receiving the first signal over the initiating link and receiving a response to the second signal over a responding link for a time period that includes a time at which the first transceiver will expect to receive the first signal.

16. The method of claim 1, wherein the process of causing the first transceiver to bundle transceiver operations that are unrelated to each other comprises:

transmit initiation link information to the second transceiver and receive irrelevant initiation link information from the second transceiver.

17. The method of claim 1, wherein:

receiving a scheduling request from the second transceiver; and

determining resource allocation information in response to the received scheduling request, the resource allocation information comprising an indicator of a future time instant at which the second transceiver should begin transmitting a first signal conveying initiation link information to the first transceiver, wherein determining the resource allocation information is based at least in part on when the first transceiver will be able to transmit a second signal conveying initiation link information to the second transceiver; and

operating the transmitter to transmit the second signal while operating the receiver to receive the first signal substantially simultaneously over a period of time that includes the future time instant.

18. The method of claim 17, wherein determining resource allocation information comprises:

detecting whether the initiating link information to be carried by the second signal is available, and if the initiating link information to be carried by the second signal is not available, waiting for the initiating link information to be carried by the second signal to become available before determining that the second transceiver should begin transmitting the first signal carrying initiating link information to the indicator of the future time instant of the first transceiver.

19. The method of claim 17, comprising:

the receiver is operated to listen for scheduling requests only at predetermined times.

20. The method of claim 17, comprising:

operating the transmitter to transmit resource allocation information to the second transceiver only at predetermined times.

21. The method of claim 17, wherein the initiating link information to be carried by the second signal is a VoIP packet.

22. An apparatus for operating a first transceiver in a packet-based communication system, the apparatus comprising:

a receiver and transmitter for bi-directional communication with a second transceiver; and

logic configured to determine an execution time for a first operation of the first transceiver based at least in part on an expected execution time for an unrelated operation of the first transceiver; and

logic configured to use the determined execution time and the expected execution time in a process that causes the first transceiver to bundle transceiver operations that are not related to each other.

23. The apparatus of claim 22, wherein the logic configured to use the determined execution time and the expected execution time in causing the first transceiver to bundle transceiver operations that are not related to each other comprises:

logic configured to cause the first transceiver to transmit bundled information, wherein the bundled information comprises initiating link information and responding link information.

24. The apparatus of claim 23, wherein the initiating link information is a data packet and the responding link information is an ACK/NAK.

25. The apparatus of claim 24, wherein the data packet is a voice over IP (VoIP) packet.

26. The apparatus of claim 22, wherein:

logic configured to determine the execution time for the first operation of the first transceiver based at least in part on the expected execution time for the unrelated operation of the first transceiver comprises:

logic configured to operate the receiver to receive a first signal from the second transceiver over an initiation link;

logic configured to determine that information carried by the first signal requires transmission of return link information to the second transceiver; and

logic configured to determine a time period during which the first transceiver may begin bundled transmission of the return link information and initiation link information that is unrelated to information carried by the first signal; and

logic configured to use the determined execution time and the expected execution time in causing the first transceiver to bundle transceiver operations that are not related to each other comprises:

logic configured to initiate the bundled transmission of the initiation link information and the return link information within the determined time period.

27. The apparatus of claim 26, wherein:

logic configured to determine a time period during which the first transceiver may begin the bundled transmission of the initiating link information and the responding link information comprises:

logic configured to detect availability of the initiating link information that is unrelated to information carried by the first signal; and

logic configured to add a predetermined response delay time to an arrival time of information carried by the first signal.

28. The apparatus of claim 27, wherein:

the information carried by the first signal is a first VoIP packet;

29. The apparatus of claim 26, comprising:

logic configured to determine a time period during which the first transceiver will expect to receive a response to the initiating link information signal;

logic configured to detect that the first transceiver should perform one or more measurements of a radio environment of the first transceiver; and

logic configured to perform a process in response to detecting that the first transceiver should perform one or more measurements of the radio environment of the first transceiver, the process comprising:

30. The apparatus of claim 26, wherein:

the information carried by the first signal is a scheduling request; and

the response link information is resource allocation information.

31. The apparatus of claim 30, wherein the initiating link information that is not related to the information carried by the first signal is a VoIP packet.

32. The apparatus of claim 30, comprising:

logic configured to perform the steps of: detecting that the initiating link information not related to information carried by the first signal is not yet available upon receiving the first signal from the second transceiver, and thus waiting for information not related to information carried by the first signal to become available before determining a period of time during which the first transceiver can begin the bundled transmission of the responding link information and the initiating link information not related to information carried by the first signal.

33. The apparatus of claim 22, wherein the logic configured to use the determined execution time and the expected execution time in causing the first transceiver to bundle transceiver operations that are not related to each other comprises:

logic configured to cause the first transceiver to receive bundled information, wherein the bundled information comprises initiating link information and responding link information.

34. The apparatus of claim 33, wherein:

the response link information is an ACK/NAK.

35. The apparatus of claim 22, wherein:

logic configured to operate the transmitter to transmit an initiate link information signal to the second transceiver;

in response to logic detecting that the first transceiver should perform one or more measurements of the radio environment of the first transceiver, performing the steps of:

36. The apparatus of claim 22, wherein:

logic configured to determine a time at which the first transceiver will expect to receive a first signal on an initiation link;

logic configured to detect that information destined for the second transceiver is available for transmission; and

logic configured to perform the steps of: determining an earlier time instant at which the first transceiver will begin transmitting a second signal carrying information destined for the second transceiver by subtracting a predetermined response delay time from the time instant at which the first transceiver will expect to receive the first signal; and

logic configured to transmit the second signal to the second transceiver at the earlier time instant; and

logic configured to perform bundled receiver operations for a time period that includes a time instant at which the first transceiver will expect to receive the first signal, wherein the bundled reception operations comprise receiving the first signal over the initiating link and receiving a response to the second signal over a responding link.

37. The apparatus of claim 22, wherein the logic configured to use the determined execution time and the expected execution time in causing the first transceiver to bundle transceiver operations that are not related to each other comprises:

logic configured to transmit initiation link information to the second transceiver and receive uncorrelated initiation link information from the second transceiver.

38. The apparatus of claim 22, wherein:

logic configured to receive a scheduling request from the second transceiver; and

logic configured to perform the steps of: responding to the received scheduling request by determining resource allocation information comprising an indicator of a future time instant at which the second transceiver should begin transmitting a first signal conveying initiation link information to the first transceiver, wherein determining the resource allocation information is based at least in part on when the first transceiver will be able to transmit a second signal conveying initiation link information to the second transceiver; and

logic configured to operate the transmitter to transmit the second signal while operating the receiver to receive the first signal substantially simultaneously for a period of time that includes the future time instant.

39. The apparatus of claim 38, wherein the logic configured to determine resource allocation information comprises:

logic configured to perform the steps of: detecting whether the initiating link information to be carried by the second signal is available, and if the initiating link information to be carried by the second signal is not available, waiting for the initiating link information to be carried by the second signal to become available before determining that the second transceiver should begin transmitting the first signal carrying initiating link information to the indicator of the future time instant of the first transceiver.

40. The apparatus of claim 38, comprising:

logic configured to operate the receiver to listen for scheduling requests only at predetermined times.

41. The apparatus of claim 38, comprising:

logic configured to operate the transmitter to transmit resource allocation information to the second transceiver only at predetermined times.

42. The apparatus of claim 38, wherein the initiating link information to be carried by the second signal is a VoIP packet.