WO2009047740A2 - Downlink assistant reference signal for resource scheduling - Google Patents

Downlink assistant reference signal for resource scheduling Download PDF

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Publication number
WO2009047740A2
WO2009047740A2 PCT/IB2008/054186 IB2008054186W WO2009047740A2 WO 2009047740 A2 WO2009047740 A2 WO 2009047740A2 IB 2008054186 W IB2008054186 W IB 2008054186W WO 2009047740 A2 WO2009047740 A2 WO 2009047740A2
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frequency band
user equipment
reference signal
downlink
manager
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PCT/IB2008/054186
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French (fr)
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WO2009047740A3 (en )
Inventor
Xiaobo Zhang
Ni Ma
Gang Wu
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Nxp B.V.
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W72/00Local resource management, e.g. wireless traffic scheduling or selection or allocation of wireless resources
    • H04W72/04Wireless resource allocation
    • H04W72/08Wireless resource allocation where an allocation plan is defined based on quality criteria
    • H04W72/085Wireless resource allocation where an allocation plan is defined based on quality criteria using measured or perceived quality
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATIONS NETWORKS
    • H04W72/00Local resource management, e.g. wireless traffic scheduling or selection or allocation of wireless resources
    • H04W72/04Wireless resource allocation
    • H04W72/0406Wireless resource allocation involving control information exchange between nodes

Abstract

A system and method for broadband multi-carrier communications. The system includes a base station, user equipment, and a transmission scheme manager. The base station transmits a downlink reference signal. The user equipment receives the downlink reference signal and acquires channel status information from the downlink reference signal for at least one available frequency band within a downlink frequency band. The transmission scheme manager is coupled to the base station and allocates a radio resource to the user equipment based on channel status feedback from the user equipment. The channel status feedback is at least partially based on the channel status information.

Description

DOWNLINK ASSISTANT REFERENCE SIGNAL FOR RESOURCE SCHEDULING

The invention relates generally to wireless communications systems, and more particularly, to downlink sounding to implement frequency domain resource scheduling for a multi-carrier system.

The 3rd Generation Partnership Project (3 GPP) was established to produce globally applicable technical specifications and technical reports for a 3rd generation mobile system based on evolved Global System for Mobile (GSM) communications core networks and the radio access technologies that they support (i.e., Universal Terrestrial Radio Access (UTRA) in both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes). The scope was subsequently amended to include the maintenance and development of the GSM technical specifications and technical reports including evolved radio access technologies (e.g., General Packet Radio Service (GPRS) and Enhanced Data rates for GSM Evolution (EDGE)).

In 3GPP Long Term Evolution (LTE) wireless communications systems, uplink (UL) sounding is used to estimate channel quality information that is provided in the form of channel quality indicators (CQI). With the trend for wireless communications to employ broader bandwidth (e.g., 20 MHz for 3GPP LTE and Worldwide Interoperability for Microwave Access (WiMAX) (based on IEEE 802.16)), channel quality can impact some or all of the available bandwidth. Compared to a traditional "narrow" band system, the wireless channel characteristics can vary tremendously on the entire bandwidth of a broadband system. Fig. 1 illustrates one example of channel status variation in a broadband system. As shown, the channel status response (shown along the vertical axis) varies over a range of frequencies (shown along the horizontal axis).

Given the variation of channel status responses over the range of frequencies, UL sounding is used to estimate channel quality information at various frequencies. In general, sounding refers to testing channels or paths by broadcasting a beacon-like Reference Signal (RS). Stations that receive the broadcast RS can evaluate the connectivity, propagation, and availability of the corresponding channel or path. The CQI for each channel, obtained from the UL Sounding Reference Signal (SRS), is then used to allocate resource blocks to User Equipment (UE). Additionally, for TDD systems, the CQI for each channel is used for beam forming.

In order to implement UL sounding, the UE sends a sounding waveform (i.e., pilot symbols) on the UL between the UE and the corresponding base station (also referred to as an evolved node B (eNB)). The eNB then measures the channel quality between the UE and the eNB. Fig. 2 illustrates a conventional UL sounding procedure in the TDD mode in terms of time domain. To begin the UL sounding procedure, the eNB requests (e.g., using a control channel 12 of a first downlink (DL) 14) the UE to sound the portion of the band that the eNB possibly uses to transmit data to the UE during a subsequent DL 16. Alternatively, the eNB may request the UE to sound the entire band in specific situations. Then, the UE sends a sounding waveform 18 in the UL 20 on the sub-carriers requested by the eNB. In this way, the eNB obtains a CQI from the sounding waveform 18. The eNB uses the CQI for resource scheduling and beam-forming (for TDD systems). In particular, according to the obtained channel parameters, the eNB reallocates the DL resources for the UE so that the UE works in those sub-carriers with better conditions. Also, for TDD systems, the eNB creates transmission weights and transmits data with the calculated weights for multiple antennas to implement beam- forming.

In addition to the UL SRS procedure described above, the 3GPP specification proposes an adaptive RS procedure. For the adaptive RS procedure (also referred to as the adaptive transmission bandwidth method), two transmission bandwidths — payload and pilot — are defined. The payload transmission bandwidth indicates the maximum transmission bandwidth of the subsequent data channel. This bandwidth is decided by UE capability, traffic load, and/or required data rate. The pilot transmission bandwidth indicates the maximum transmission bandwidth of the pilot channel for the CQI measurement. This bandwidth is equal to or wider than the payload transmission bandwidth. Additionally, the pilot transmission bandwidth is determined based on the channel conditions, UE capability, and traffic load. Exemplary channel conditions include path loss, signal-to-interference plus noise power ratio (SINR), and so forth. Based on the reported information related to the UEs, the eNB allocates a frequency band to each UE for a corresponding pilot channel. According to the allocated frequency bands, the UEs transmit pilot signals. Fig. 3 shows an example of the pilot channel transmission 30 and data channel assignment based on frequency-domain channel dependent scheduling with adaptive pilot transmission bandwidth.

Both the UL SRS and the adaptive RS schemes implement a UL RS to perform the CQI measurement. Depending on the bandwidth of the pilot channel, the UL SRS scheme exhibits certain disadvantages. If a wideband pilot channel is used for the CQI measurement (or sounding), then the throughput is potentially reduced due to overuse of the RS resource. Also, the UL SRS procedure results in substantial interference to other cells and, hence, CQI measurement error due to a decreased pilot power density. In contrast, if a narrowband pilot channel is used for the CQI measurement (or sounding), then the eNB cannot optimize the resource allocation over the entire bandwidth.

The adaptive RS scheme also exhibits certain disadvantages. If an adaptive -band pilot channel is used for the CQI measurement (or sounding), then the eNB cannot accurately decide the pilot bandwidth allocated for the UE because the eNB cannot know the exact path loss of each UE, and the SINR of the UL and the DL are not the same.

A system and method for broadband multi-carrier communications is described. The system includes a base station, user equipment, and a transmission scheme manager. The base station transmits a downlink reference signal. The user equipment receives the downlink reference signal and acquires channel status information from the downlink reference signal for at least one available frequency band within a downlink frequency band. The transmission scheme manager is coupled to the base station and allocates a radio resource to the user equipment based on channel status feedback from the user equipment. The channel status feedback is at least partially based on the channel status information. Embodiments of this system, and the accompanying methods, provide improved sounding performance compared to convention uplink sounding techniques. Additionally, higher transmission efficiency may be achieved because the resources occupied by the downlink reference signal are less than the resources occupied by the uplink sounding techniques. Also, implementing embodiments of a downlink sounding technique can help to save control signaling. Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

Fig. 1 illustrates one example of channel status variation in a conventional broadband system.

Fig. 2 illustrates a conventional uplink sounding procedure in the time division duplex mode in terms of time domain.

Fig. 3 illustrates an example of conventional pilot channel transmission and data channel assignment based on frequency-domain channel dependent scheduling with adaptive pilot transmission bandwidth.

Fig. 4 illustrates a schematic block diagram of one embodiment of a wireless communications system that may implement a broadband multi-channel system.

Fig. 5 illustrates a schematic block diagram of a more detailed embodiment of the transmission resource manager of the wireless communications system of Fig. 4. Fig. 6 illustrates a schematic block diagram of a more detailed embodiment of the user equipment of the wireless communications system of Fig. 4.

Fig. 7 illustrates one embodiment of a downlink sounding procedure that sends a downlink reference signal on the entire downlink frequency band.

Figs. 8A and 8B illustrate one embodiment of another downlink sounding that sends a downlink reference signal on selected frequency bands of the downlink frequency band.

Fig. 9 illustrates a schematic flow chart diagram of one embodiment of a method for downlink sounding in a wireless communications system.

Fig. 10 illustrates a schematic flow chart diagram of another embodiment of method for downlink sounding that uses the entire downlink frequency band.

Fig. 11 illustrates a schematic flow chart diagram of another embodiment of a method for downlink sounding that uses selected frequency bands of the downlink frequency band.

Throughout the description, similar reference numbers may be used to identify similar elements. A technique, according to an embodiment, for allocating radio resources in a broadband multi-carrier system involves using a downlink (DL) reference signal (RS), instead of a conventional uplink (UL) RS. While a conventional base station (eNB) uses a special RS such as the UL Sounding RS (SRS) proposed by 3GPP LTE, current 3GPP UL SRS only supports resource scheduling within a small range in the frequency domain, and using too many UL SRSs significantly reduces transmission efficiency. Accordingly, embodiments of a DL RS scheme and corresponding frame structure are implemented to support resource scheduling within the entire available frequency domain for broadband multi-carrier systems such as 3GPP LTE. As a matter of nomenclature, the DL RS described herein is also referred to as an Assistant RS (ARS).

In an embodiment, the eNB uses a broadcasting format over a broad bandwidth to transmit the DL RS. The DL RS may be transmitted on the entire DL frequency band (i.e., the entire frequency spectrum used for DL data transmissions) or on selected DL frequency bands. The mobile stations, or user equipment (UE), are then able to acquire channel status information (CSI) for all of the applicable DL frequency bands and feed channel status feedback (e.g., the channel quality indicators (CQIs) or preferred bands) back to the eNB so that the eNB can reallocate the radio resources.

Fig. 4 illustrates a schematic block diagram of one embodiment of a wireless communications system 100 that may implement a broadband multi-channel system. The illustrated wireless communications system 100 includes a base station 102, or an evolved Node B (eNB), and multiple mobile stations 104, or user equipment (UE). The wireless communications system 100 may be operated in various modes, including multiuser multiple-input multiple-output (MU-MIMO) mode.

In the illustrated embodiment, the eNB 102 includes four antennas 106, although the eNB 102 can include more than four antennas 106. The eNB 102 also includes a transmission resource manager 110. In general, the eNB 102 is responsible for managing transmission resources of the wireless communications system 100. One example of the transmission resource manager 110 is shown in Fig. 5 and described in more detail below. In one embodiment, the UEs 104 are wireless communications mobile stations that support wireless operation as specified in the 3GPP LTE specification. The UEs 104 may have one or two antennas 108, although the UEs 104 are not limited to two antennas 108 (e.g., the UEs 104 can include more than two antennas 108). Other embodiments of the wireless communications system 100 may implement other wireless schemes for broadband multi-carrier systems such as WiMAX. In order to schedule radio resources within the wireless communications system

100, the eNB 102 transmits a DL RS to one or more UEs 104. The UEs 104 receive the DL RS and acquire channel status information (CSI) from the DL RS for at least one available frequency band within a DL frequency band. The UE 104 then generates channel status feedback that is at least partially based on the CSI and transmits the channel status feedback to the eNB 102. As explained in more detail below, the channel status feedback may be quantized channel quality indicators (CQIs) for one or more of the available frequency bands within the DL frequency band. Alternatively, the channel status feedback may be the CQIs for all of the frequencies in the DL frequency band. In some embodiments, the channel status feedback is a preferred radio resource indicator indicative of a preferred radio resource for the transmitting UE 104. Other embodiments may use other types of channel status feedback from the UEs 104 to the eNB 102. The eNB 102 then uses the channel status feedback to allocate a radio resource to the transmitting UE 102. For example, the eNB 102 may allocate a preferred sub-carrier to the UE 102 in response to channel status feedback from the UE 102 that indicates the preferred sub-carrier.

Fig. 5 illustrates a schematic block diagram of a more detailed embodiment of the transmission resource manager 110 of the wireless communications system 100 of Fig. 4. Although the depicted transmission resource manager 110 includes several functional blocks described herein, other embodiments of the transmission resource manager 110 may include fewer or more functional blocks to implement more or less functionality.

The illustrated transmission resource manager 110 includes a resource block manager 112, an antenna manager 114, a transmission scheme manager 116, and a DL RS manager 118. The transmission scheme manager 110 is coupled to the eNB 102. In general, the transmission resource manager 110 facilitates allocation of a radio resource to the UE 104 based on the channel status feedback from the UE 104. In one embodiment, the resource block manager 112 is responsible for identifying resources, or resource blocks, that are available for baseband transmission. In particular, the resource block manager 112 identifies at least one available frequency band within the DL frequency band. Resources, or resource blocks, may refer to frequency blocks in the frequency domain and/or time blocks in the time domain.

In one embodiment, the antenna manager 114 is responsible for identifying antennas 106 of the eNB 102 that are available for baseband transmissions. Among other things, the antennas 106 transmit the DL RS to one or more UEs 104.

In one embodiment, the transmission scheme manager 116 is responsible for establishing a transmission scheme for the UEs 104. The transmission scheme defines both the allocation of available resources, or resource blocks, and the selection of available antennas 106 amongst the UEs 104. More specifically, the transmission scheme manager 116 facilitates allocation of radio resources to the UEs 104 based on the channel status feedback from the UE 104. In one embodiment, the DL RS manager 118 is responsible for managing the generation of the DL RS signal. Additionally, the DL RS manager 118 is responsible for providing notification of the DL RS to the UEs 104. In order to implement this functionality, the illustrated DL RS manager 118 includes a DL frequency manager 120 and a notification manager 122. In one embodiment, the DL frequency manager 120 selects at least one frequency band of the available frequency bands as a selected frequency band for transmission of the DL RS to the UE 104. Some embodiments of the DL frequency manager 120 select the entire DL frequency band as the selected frequency band for transmission of the DL RS to the UE 104 (as shown in Fig. 7 and described in more detail below), while other embodiments of the DL frequency manager 120 use one or more selected frequency bands corresponding to less than the entire DL frequency band. In other words, the selected frequency bands are narrower than the entire DL frequency band. Where the DL frequency manager 120 transmits the DL RS on more than one selected frequency band, the multiple selected frequency bands may be noncontiguous. Additionally, in an embodiment, the DL frequency manager 120 selects different frequency bands, or sets of frequency bands, for different transmissions (e.g., consecutive transmissions) of the DL RS. As an example, the DL frequency manager 120 may select a first set of selected frequency bands for a first DL RS transmission and then select the remaining frequency bands (i.e., other than the first set of selected frequency bands) for another, subsequent DL RS transmission. In this way, the DL frequency manager 120 may select the entire DL frequency band over the course of time — at different times for different DL RS transmissions. An illustration of this example is shown in Figs. 8A and 8B and described in more detail below.

The notification manager 122 facilitates a notification to the UE 104 of the selected frequency band used by the eNB 102 for the DL RS transmission. In one embodiment, the eNB 102 sends a notification of the selected DL frequency band(s) to the UEs 104 in a DL control channel. In order to facilitate this type of notification, the notification manager 122 includes a control signal generator 124. In particular, the control signal generator 124 generates notification information for transmission in a DL control signal to the UE 104 to notify the UE 104 of the selected frequency band(s) for transmission of the DL RS.

In another embodiment, the eNB 102 sends a notification of the selected DL frequency band(s) to the UEs 104 in a special code sequence transmitted with, or as a part of, the DL RS. The UEs 104 then identify the special code sequence with the DL RS using, for example, a correlation computation or another known code identification technique. In order to facilitate this type of notification, the notification manager 122 includes a code generator 126. In particular, the code generator 126 generates the special code sequence for transmission with the DL RS to the UE 104 to notify the UE 104 of the selected frequency band(s) for transmission of the DL RS.

Fig. 6 illustrates a schematic block diagram of a more detailed embodiment of the UE 104 of the wireless communications system 100 of Fig. 4. Although the depicted UE 104 includes several functional blocks described herein, other embodiments of the UE 104 may include fewer or more functional blocks to implement more or less functionality.

The illustrated UE 104 includes a channel status manager 132, which includes a channel quality indicator (CQI) generator 134, and a channel feedback manager 136. In one embodiment, the channel status manager 132 acquires the CSI of applicable frequency bands from the DL RS. As an example, the channel status manager 132 may invoke the CQI generator 134 to generate the CQI for one or more frequency bands. However, although CQIs are described as one form of CSI, other forms of CSI can be used in establishing a transmission scheme. Additionally, it should be noted that the DL CSI may be used to estimate the UL CSI because of channel reciprocity in TDD systems.

The channel feedback manager 136 generates the channel status feedback based on the CSI to send to the eNB 102. Since the DL RS scheme relies on implementations in which the channel characteristics are first acquired by the UEs 104, the UEs 104 send the channel status feedback to the eNB 102 to notify the eNB 102 about the DL CSI. In this way, the eNB 102 receives the DL CSI information for use in scheduling the radio resources for the UEs 104.

Depending on the implementation of the UEs 104, the channel feedback manager 136 may send different types of information to the eNB 102 as channel status feedback. In one embodiment, the channel feedback manager 136 sends the quantized CQIs to the eNB 102 so that the eNB 102 can allocate the radio resources based on the CQIs.

However, this type of feedback and allocation may produce substantial information since the CQIs of all of the bandwidth including the DL RS is sent from the UEs 104 to the eNB 102. Alternatively, the channel feedback manager 136 may send the quantized CQIs for less than all of the bandwidth that includes the DL RS. In another embodiment, the channel feedback manager 136 determines one or more preferred radio resources for the UE 104 based on the CQIs generated by the CQI generator 134. The UE 104 then sends channel status feedback to the eNB 102 to indicate the preferred radio resources (compared to current occupied resources) of the UE 104. The eNB 102 then performs resource scheduling according to the preferred radio resource indicator included in the channel status feedback. The preferred radio resource indicator is indicative of the preferred radio resource for the UE 104. This feedback and allocation scheme may consume a limited number of bits.

As described in some detail above, there are two candidate methods for the eNB 102 to set the DL RS bandwidth. In one embodiment, the eNB 102 transmits the DL RS over the entire DL frequency band. Alternatively, the eNB 102 transmits the DL RS over one or more selected DL frequency bands corresponding to less than the entire DL frequency band. As an example of the latter frequency selection, the eNB 102 may transmit the DL RS over selected frequency bands that are unsatisfactory for current transmission quality.

Fig. 7 illustrates one embodiment of a DL sounding procedure 140 that sends a DL RS 142 on the entire DL frequency band. In particular, the DL RS 142 is transmitted from the eNB 102 to the UEs 104 during a DL period 144, prior to a UL period 146. By transmitting the DL RS 142 over the entire DL bandwidth, the UEs 104 can monitor the CQIs on all of the DL frequency bands. However, it should be noted that, although the eNB 102 may be implemented to transmit the DL RS 142 over the entire DL frequency band, some implementations may result in reduced transmission efficiency and/or increased scheduling complexity. For example, the sub-carriers of one of the UEs 104 on "good" transmission status may be reallocated to other UEs 104 within the wireless communications system 100.

Figs. 8A and 8B illustrate one embodiment of another DL sounding procedure 140a and 140b that sends a DL RS 142 on selected frequency bands of the DL frequency band. For each DL RS transmission, the unselected frequency bands are not assumed to reallocate. For example, unselected sub-carriers may already have "good" transmission status with one of the UEs 104 within the wireless communications system 100. In this way, the UEs 104 may limit monitoring to the selected frequency bands. Additionally, the UEs 104 may apply for the corresponding radio resources, but not for the radio resources corresponding to the unselected frequency bands.

In one embodiment, a minimum bandwidth of the DL RS 142 is established by the eNB 102. As an example, the minimum bandwidth of the DL RS 142 may be set at 375 KHz. As another example, the minimum bandwidth of the DL RS 142 may be set at 1.25 MHz. Other embodiments may use other minimum bandwidths.

In an embodiment, the DL sounding procedure 140a and 140b may cover the entire DL frequency band by transmitting the DL RS 142 on alternating selected frequency bands. For example, Fig. 8 A shows the DL RS 142 transmitted on low and mid-high frequency bands, while Fig. 8B shows a subsequent DL RS 142 transmitted on the remaining mid-low and high frequency bands. In this way, the eNB 102 may cover the entire DL frequency band over two or more sequential (e.g., consecutive) DL RS transmissions.

Fig. 9 illustrates a schematic flow chart diagram of one embodiment of a method 150 for DL sounding in a wireless communications system 100. Although the DL sounding method 150 is described in relation to the wireless communications system 100 of Fig. 1, other embodiments may be implemented in conjunction with other wireless communications systems. At block 152, the eNB 102 transmits a DL RS to the UEs 104. At block 154, the UEs 104 acquire the CSI of the channels, or selected DL frequency bands, that include the DL RS. At block 156, the UEs 104 send channel status feedback to the eNB 102. As described above, embodiments of the channel status feedback include, but are not limited to, CQIs of the selected DL frequency bands and/or a preferred radio resource indicator for the corresponding UE 104. At block 158, the eNB 102 allocates one or more radio resources to the UEs 104 based on the channel status feedback received from each UE 104. The depicted DL sounding method 150 then ends. Other embodiments of the DL sounding method 150 may include other operations related to resource scheduling in the wireless communications system 100. For example, some embodiments of the DL sounding method 150 include notifying the UEs 104 of the selected DL frequency bands for the DL RS transmission. In particular, the eNB 102 may send a DL control signal to the UEs 104. Alternatively, the eNB 102 may send a special code sequence in conjunction with the DL RS.

Fig. 10 illustrates a schematic flow chart diagram of another embodiment of method 150 for DL sounding that uses the entire DL frequency band. At block 152a, the eNB 102 transmits a DL RS to the UEs 104 on all frequencies within the DL frequency band. The UEs 104 then acquire the CSI as described above. Then, at block 156a the UEs 104 send the CQIs for all of the selected frequency bands to the eNB 102 so that the eNB 102 can allocate the radio resources to the UEs 104 as described above. The depicted embodiment of the DL sounding method 150 then ends.

Fig. 11 illustrates a schematic flow chart diagram of another embodiment of a method 150 for DL sounding that uses selected frequency bands of the DL frequency band. At block 152b, the eNB 102 transmits a DL RS to the UEs 104 on selected DL frequency bands within the entire DL frequency band. The UEs 104 then acquire the CSI as described above. Then, at block 156b the UEs 104 determine a preferred radio resource for each UE 104 and send preferred radio resource indicators to the eNB 102 so that the eNB 102 can allocate the preferred radio resources to the UEs 104 as described above. The depicted embodiment of the DL sounding method 150 then ends. Embodiments of the DL RS scheme and frame structure can be used to schedule resources on any type of broadband multi-carrier system. Additionally, embodiments of the DL RS scheme and frame structure can be used to schedule resources over the entire DL frequency band. Moreover, embodiments of the DL RS scheme and frame structure may maintain a relatively high transmission efficiency, occupy relatively few resources, and/or limit the impact of control signals used to notify UEs 104 of selected DL frequency bands.

Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts as described and illustrated herein. The invention is limited only by the claims.

Claims

What is claimed is:
1. A method for allocating radio resources in a broadband multi-carrier system, the method comprising: transmitting a downlink reference signal from a base station to user equipment within the broadband multi-carrier system; acquiring channel status information from the downlink reference signal for at least one available frequency band within a downlink frequency band of the broadband multi-carrier system; and allocating radio resources within the broadband multi-carrier system based on channel status feedback from the user equipment to the base station, wherein the channel status feedback is at least partially based on the channel status information.
2. The method of claim 0, wherein transmitting the downlink reference signal comprises transmitting the downlink reference signal on the entire downlink frequency band of the broadband multi-carrier system.
3. The method of claim 0, wherein transmitting the downlink reference signal comprises transmitting the downlink reference signal on a selected frequency band of the downlink frequency band, wherein the selected frequency band is narrower than the entire downlink frequency band.
4. The method of claim 0, wherein transmitting the downlink reference signal further comprises transmitting the downlink reference signal on multiple noncontiguous selected frequency bands of the downlink frequency band.
5. The method of claim 0, further comprising transmitting another downlink reference signal in a subsequent downlink reference signal transmission on at least one remaining frequency band other than the multiple noncontiguous selected frequency bands, wherein a combination of the selected frequency bands and the at least one remaining frequency band cover the entire downlink frequency band of the broadband multi-carrier system.
6. The method of claim 0, further comprising transmitting notification information in a downlink control signal from the base station to the user equipment to notify the user equipment of a selected frequency band of the downlink reference signal.
7. The method of claim 0, further comprising transmitting a special code sequence within the downlink reference signal to notify the user equipment of a selected frequency band of the downlink reference signal.
8. The method of claim 0, further comprising transmitting the channel status feedback from the user equipment to the base station, wherein acquiring the channel status information from the downlink reference signal comprises acquiring the channel status information from the downlink reference signal at the user equipment.
9. The method of claim 0, further comprising: quantizing channel quality indicators at the user equipment for all sub-carriers that include the downlink reference signal; and transmitting the channel quality indicators for all of the sub-carriers from the user equipment to the base station.
10. The method of claim 0, further comprising: quantizing a channel quality indicator at the user equipment for a sub-carrier that includes the downlink reference signal; determining a preferred radio resource for the user equipment based on the channel quality indicator; and transmitting a preferred radio resource indicator from the user equipment to the base station to indicate the preferred radio resource of the user equipment to the base station.
11. A system for broadband multi-carrier communications, the system comprising: a base station to transmit a downlink reference signal; user equipment to receive the downlink reference signal and to acquire channel status information from the downlink reference signal for at least one available frequency band within a downlink frequency band; and a transmission scheme manager coupled to the base station, the transmission scheme manager to allocate a radio resource to the user equipment based on channel status feedback from the user equipment, wherein the channel status feedback is at least partially based on the channel status information.
12. The system of claim 0, wherein the user equipment comprises: a channel status manager to acquire the channel status information from the downlink reference signal; and a channel feedback manager coupled to the channel status manager, the channel feedback manager to generate the channel status feedback based on the channel status information.
13. The system of claim 0, wherein the user equipment further comprises a channel quality indicator generator coupled to the channel status manager, the channel quality indicator generator to quantize a channel quality indicator for the at least one available frequency band within the downlink frequency band.
14. The system of claim 0, wherein: the channel feedback manager is further configured to determine a preferred radio resource for the user equipment based on the channel quality indicator; and the user equipment is further configured to transmit a preferred radio resource indicator to the base station, wherein the preferred radio resource indicator is indicative of the preferred radio resource for the user equipment.
15. The system of claim 0, wherein the base station comprises: a resource block manager to identify the at least one available frequency band within the downlink frequency band; a downlink frequency manager coupled to the resource block manager, the downlink frequency manager to select at least one frequency band of the available frequency bands as a selected frequency band for transmission of the downlink reference signal to the user equipment; and a notification manager coupled to the downlink frequency manager, the notification manager to facilitate a notification to the user equipment of the selected frequency band.
16. The system of claim 0, wherein the downlink frequency manager is further configured to select the entire downlink frequency band as the selected frequency band for transmission of the downlink reference signal to the user equipment.
17. The system of claim 0, wherein the base station further comprises a control signal generator coupled to the notification manager, the control signal generator to generate notification information for transmission in a downlink control signal to the user equipment to notify the user equipment of the selected frequency band for transmission of the downlink reference signal.
18. The system of claim 0, wherein the base station further comprises a code generator coupled to the notification manager, the code generator to generate a special code sequence for transmission with the downlink reference signal to the user equipment to notify the user equipment of the selected frequency band for transmission of the downlink reference signal.
19. An apparatus for use as a base station in a broadband multi-carrier system, the apparatus comprising: an antenna to transmit a downlink reference signal; a downlink frequency manager coupled to the antenna, the downlink frequency manager to select at least one frequency band within a downlink frequency band as a selected frequency band for transmission of the downlink reference signal; and a transmission scheme manager coupled to the antenna, the transmission scheme manager to receive channel status feedback via the antenna and to allocate a radio resource for user equipment based on the channel status feedback.
20. The apparatus of claim 0, further comprising a notification manager coupled to the downlink frequency manager, the notification manager to facilitate a notification via the antenna to the user equipment of the selected frequency band for transmission of the downlink reference signal.
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