WO2008140827A1 - Simultaneous messaging from multiple sources using hierarchical modulation - Google Patents

Abstract

Various example embodiments are disclosed. An example method includes receiving a signal (904). The received signal includes a first sub-signal from a first source, the first sub-signal including a first codeword representing a first message. The first codeword including a first plurality of data symbols. The received signal also includes a second sub-signal from a second source, the second sub-signal including a second codeword representing a second message. The second codeword includes a second plurality of data symbols and is received substantially simultaneously with the first sub-signal. The example method further includes demodulating the received signal using hierarchical modulation to determine the first codeword and the second codeword by determining, respectively, the first plurality of data symbols and the second plurality of data symbols (906). The example method still further includes decoding the first codeword to determine the first message (908) and decoding the second codeword to determine the second message (910).

Description

SIMULTANEOUS MESSAGING FROM MULTIPLE SOURCES USING HIERARCHICAL MODULATION

Inventors:

Aik Chindapol,

Jacob Hoydis, and

Nikolaj Marchenko

PRIORITY CLAIM

[0001] This application claims the benefit of U.S. Provisional Patent Application

No. 60/917,707, filed May 14, 2007, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD [0002] This description relates to wireless networks.

BACKGROUND

[0003] In wireless networks, relay stations (or relay stations) may extend the coverage range of the network. Relay stations may, for example, receive and forward data between a source station and a destination station (e.g., a subscriber station). Relay stations may be used in, for example, IEEE 802.16 WiMax networks, 802.11 WLAN networks, or cellular telephone networks. Relay stations and/or destination stations and/or source stations may provide feedback such as acknowledgements (ACKs) or negative acknowledgments (NACKs) for received data packets to provide for reliable communications.

SUMMARY

[0004] In an example embodiment, a method for data communication in a wireless network may include receiving a signal, where the signal may be a combined signal. In the example method, the received signal may include a first sub-signal from a first source, the first sub-signal including a first codeword representing a first message, the first codeword including a first plurality of data symbols. The received signal may also include a second sub-signal from a second source, the second sub-signal including a second codeword representing a second message where the second codeword includes a second plurality of data symbols. The second sub-signal may be received substantially simultaneously with the first sub-signal, e.g., in a same time slot.

[0005] The example method may also include demodulating the received signal using hierarchical modulation to determine the first codeword and the second codeword. The first and second codewords may be ascertained by determining, respectively, the first plurality of data symbols and the second plurality of data symbols. Corresponding data symbols of the first plurality and second plurality may be determined separately or concurrently. The example method may also include decoding the first codeword to determine the first message and decoding the second codeword to determine the second message.

[0006] In another example embodiment, a method for data communication in a wireless network may include sending a data packet to both a relay station and a destination station in the wireless network. The example method may also include receiving a combined signal (e.g., in response to the packet). The combined signal may include a first sub-signal from the relay station, the first sub-signal including one of a relay station acknowledgment (ACK) and a relay station negative acknowledgment (NACK) for the data packet. In the example method, the first sub-signal may be received during an ACK/NACK frame corresponding with the data packet. The relay station ACK may acknowledge successful receipt of the data packet by the relay station, while the relay station NACK may acknowledge unsuccessful receipt of the data packet by the relay station.

[0007] The combined signal may also include a second sub-signal from the destination station, where the second sub-signal includes one of a destination station acknowledgment (ACK) and a destination station negative acknowledgment (NACK) for the data packet. The second sub-signal may also be received during the ACK/NACK frame corresponding with the data packet and may be received substantially simultaneously with the first sub-signal. In the example method, the destination station ACK acknowledges successful receipt of the data packet by the destination station and the destination station NACK acknowledges unsuccessful receipt of the data packet by the destination station.

[0008] The example method may further include demodulating the combined signal using hierarchical modulation to determine whether the relay station sent the relay station ACK or the relay station NACK, and whether the destination station sent the destination station ACK or the destination station NACK. The ACK/NACKs from the relay station and destination station may be sent as codewords, which are then decoded to determine which of the acknowledgments (ACK or NACK) were sent, respectively, from the relay station and the destination station.

[0009] In yet another example embodiment, an apparatus, e.g., for wireless communication, may include a wireless transceiver, a processor coupled with the transceiver and a memory coupled with the processor. The transceiver, processor and memory may be collectively configured to implement example methods, such as those described above, and/or those described in the following description.

[0010] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a block diagram illustrating an example embodiment of a wireless network.

[0012] FIG. 2 is a diagram illustrating an example embodiment of hierarchical modulation/demodulation.

[0013] FIG. 3 is a diagram illustrating a constellation diagram that may be used in an example embodiment.

[0014] FIG. 4 is a block diagram illustrating an example embodiment of a subchannel.

[0015] FIG. 5 is a block diagram illustrating an example embodiment of a subchannel tile that may be used in the subchannel of FIG. 4 and an example embodiment of an associated constellation diagram. [0016] FIG. 6 is a table illustrating vector indices that may be used for coding and decoding ACKs and/or NACKs in an example embodiment.

[0017] FIG. 7 is a table illustrating example embodiments of codewords for a destination station ACK and a destination station NACK using the vector indices illustrated in FIG. 6.

[0018] FIG. 8 is a table illustrating example embodiments of codewords for a relay station ACK and a relay station NACK using the vector indices illustrated in FIG. 6.

DETAILED DESCRIPTION

[0019] An example wireless relay network may include a source station, one or more relay stations, and one or more destination stations or subscriber stations. The relay stations may, for example, extend the range or coverage area and/or capacity of the source station by receiving and forwarding data between the source station and the one or more destination stations. Or, the relay stations may retransmit packets which were sent by the source station and successfully received by the relay station but not by the destination station, or which were sent by the destination station and successfully received by the relay station but not by the source station. The relay network may include one "hop," in which the one or more relay stations receive and forward the data directly to and from the source station and destination station, or multiple hops, in which the relay stations may receive the data from and/or forward the data to other relay stations in the wireless relay network. While the techniques discussed herein are generally described with reference to example embodiments for ACK and NACK messaging in a wireless network, it will be appreciated that the described example techniques may be applied to other types of messaging (or signaling) in any number of wireless network configurations.

[0020] FIG. 1 is a block diagram of a wireless network 102 according to an example embodiment. According to this example, the wireless network 102 may include a network in which a plurality of stations communicate via an air interface, such as an IEEE 802.16 WΪMax network, an IEEE 802.11 WLAN network, or a cellular telephone network, as non-limiting examples. While the example shown in FIG. 1 shows a single source station 104, a single relay station 106, and a single destination station 108, any number of source stations 104, relay stations 106, and destination stations 108 may be included in the wireless network 102.

[0021] The source station 104 may include an 802.16 source station, an 802.11 access point, a cellular source station (e.g., base station), or a node B, according to various example embodiments. The relay station 106 may be configured to receive and forward messages or packets or bursts between the source station 104 and the destination station 108, or to retransmit packets which were not successfully received by either the source station 104 or the destination station 108. The relay station 106 may be mobile or may be fixed in position. The destination station 108 may include a cellular phone, smartphone, personal digital assistant (PDA), notebook computer, or other wireless device or subscriber station, according to example embodiments.

[0022] In the wireless network 102, the source station may transmit a packet to the relay station 106, which may be forwarded to the destination station 108 by the relay station, in an example embodiment. As is also shown in FIG. 1, the packet may be sent directly to the destination station 108 from the source station 102 (e.g., instead of being forwarded by the relay station 106). In such an approach, the packet may still be sent to the relay station 106 as well, such as for forwarding to other destination stations operating in the network. Alternatively, the packet may simply be "overheard" by the relay station.

[0023] In response to receiving the packet, the relay station 106 and the destination station 108 may decode the packet and determine if any errors exist in the packet that cannot be corrected, such as using error correction codes, for example. If the packet is received without error, or any errors are able to be corrected, the relay station 106 and/or the destination station 108 may provide a respective positive acknowledgment (ACK) message to the source station 104 indicating the packet was successfully received. If, however, the packet is received with an error that cannot be corrected, the relay station 106 and/or the destination station 108 may provide a respective negative acknowledgment to the source station 104 indicating the packet was not successfully received.

[0024] It will be appreciated that any combination of ACKs and NACKs may be received from the relay station 106 and the destination station 108 in this example. For instance, both the relay station 106 and the destination station 108 may successfully receive the packet, and may then both provide respective ACK messages to the source station 104. Alternatively, both the relay station 106 and the destination station 108 may unsuccessfully receive the packet, and may then both provide NACK messages to the source station 104. As still another alternative, one of the relay station 106 and the destination station 108 may successfully receive the packet while the other my unsuccessfully receive the packet. In this situation, that station that successfully received the packet would provide an ACK message to the source station 104, while the station that unsuccessfully received the packet would provide a NACK message to the source station 104.

[0025] In the wireless network 102 illustrated in FIG. 1 , the ACK/NACK messages to the source station 104 from the relay station 106 and the destination station 108 may be communicated in a substantially simultaneous fashion, such as using hierarchical modulation. In an example embodiment using hierarchical modulation, the destination station may transmit a first plurality of data symbols to the source station 104, where the first plurality of data symbols includes an ACK/NACK message from the destination station or a codeword representing the destination station ACK/NACK message. The relay station 106 may substantially simultaneously transmit a second plurality of data symbols to the source station 104, where the second plurality of data symbols includes an ACK/NACK message from the relay station or a codeword representing the relay station ACK/NACK message. In such an approach, the first plurality of data symbols may be sent at a first amplitude (e.g., according to a first constellation diagram), while the second plurality of data symbols may be sent at a second amplitude (e.g., according to a first diagram).

[0026] FIG. 2 is a diagram that illustrates an example of constellation diagrams that may be used in an example embodiment of hierarchical modulation. The example embodiment in FIG. 2 will be described with further reference to FIG. 1. It is noted that while the constellation diagrams illustrated in FIG. 2 illustrate an embodiment where the destination station 108 and the relay station 106 use a common modulation scheme (e.g., Quadrature Phase-Shift Keying (QPSK)) for transmitting data symbols, in other embodiments the destination station 108 and the relay station 106 may use different modulation schemes. For example, the destination station 108 may transmit data symbols in accordance with QPSK, while the relay station may transmit data symbols in accordance with another modulation scheme, such as 16 Quadrature Amplitude Modulation (16-QAM) or 64-QAM, as two examples.

[0027] As will be discussed in further detail below, the ACK/NACK messages from the relay station 106 and the destination station 108 may be sent using a plurality of data symbols (such as included in codewords). Each of those data symbols may be transmitted using the techniques described with respect to FIGs. 2-5. Associated codewords may then decoded (e.g., by the source station 104) once each of the plurality of symbols are determined, e.g., by demodulating hierarchically modulated signals. For instance, the relay station 106 and the destination station 108 may substantially simultaneously transmit data symbols of ACK/NACK messages during an ACK/NACK frame associated with a received data packet to generate such hierarchically modulated signals. The ACK/NACK frame may be assigned in a control message included in the data packet.

[0028] In FIG. 2, a constellation diagram 200 illustrates QPSK constellation points Mo, Mi, M₂ and M₃. Signals corresponding with these constellation points may be used by the destination station 108 to transmit data symbols to the source station 104 in accordance with the hierarchical modulation scheme shown in FIG. 2. As is known, the QPSK constellation points in the constellation diagram 200 each represent two bits of data. In one example, the point M₀ may represent data bits of 00, the point Mi may represent data bits of 01, the point M₂ may represent data bits of 10 and the point M3 may represent data bits of 11. However, depending on the particular embodiment, the data bits represented by each of the data symbols in the constellation diagram 200 may be any appropriate arrangement of the four values that can be represented by two bits of data (i.e., 00, 01, 10 and 11).

[0029] The constellation diagram 210 in FIG. 2 illustrates QPSK constellation points R₀, Ri, R₂ and R₃. Signals corresponding with these constellation points may be used by the relay station 106 to transmit data symbols to the source station 104 in accordance with the hierarchical modulation scheme shown in FIG. 2. As shown in FIG. 2, the constellation points in the constellation diagram 210 represent data symbols transmitted with lower amplitudes than the data symbols represented by the constellation points in the constellation diagram 200. As with the constellation points in the constellation diagram 200, the constellation points in the constellation diagram 210 may represent any appropriate arrangement of the four values that can be represented by two bits of data (i.e., 00, 01, 10 and 11).

[0030] The constellation diagram 220 in FIG. 2 illustrates the combination of the constellation diagrams 200 and 210. In the constellation diagram 220, the constellation diagram 210 is superimposed on the constellation diagram 200. Because the data symbols represented by the constellation points in the constellation diagram 210 are transmitted at lower amplitude than the data symbols represented by the constellation points in the constellation diagram 200, the resulting (combined) signal received, e.g., at the source station 104 will include sixteen possible constellation points, as illustrated by the constellation diagram 220.

[0031] For instance, if the destination station transmits a data symbol corresponding with the constellation point Mo shown in the constellation diagram 200 and the relay station 106 transmits a data symbol corresponding with the constellation point Ro shown in the constellation diagram 210, the combined signal received at the source station 104 will correspond with the constellation point Ro shown in the constellation diagram 220. As shown, this signal has higher I and Q components than the Mo signal alone due the combination of the Ro signal with the Mo signal.

[0032] Similarly, if the destination station transmits a data symbol corresponding with the constellation point M₀ shown in the constellation diagram 200 and the relay station 106 transmits a data symbol corresponding with the constellation point R₃ shown in the constellation diagram 210, the combined signal received at the source station 104 will correspond with the constellation point R₃ shown in the constellation diagram 220. This signal has a higher I component and a lower Q component than the M₀ signal alone due the combination of the R₃ signal with the Mo signal.

[0033] FIG. 3 is a diagram illustrating a constellation diagram 300 for an example embodiment of hierarchical modulation where two QPSK signals at different amplitudes are combined and received at a wireless node, such as the source station 104. The constellation diagram 300 is an example embodiment of the constellation diagram 220 of FIG. 2 (i.e., the superimposition of the constellation diagram 210 with the constellation diagram 200).

[0034] In the constellation diagram 300, the first two data bits represent the data bits for the symbols Mo, Mi, M₂ and M3 shown in the legend, which correspond with the arrangement illustrated for the constellation diagram 200 of FIG. 2. The second two data bits for each of the constellation points of the constellation diagram 300 represent the data bits for the symbols Ro, Ri, R₂ and R3 shown in the legend, which correspond with the arrangement illustrated for the constellation diagram 210 of FIG. 2. Thus, the two data symbols of such a hierarchically modulated signal may be determined by demodulating the combined signal to determine which of the sixteen points in the constellation diagram is represented by the combined signal. Various approaches for such demodulation may be used.

[0035] In an example embodiment implementing a hierarchical modulation scheme such as the one illustrated in FIGs. 2 and 3 and discussed above, a received signal, Y, for two received data symbols (e.g., one of (Mo, Mi, M₂ and M₃) and one of (Ro, Ri, R₂ and R₃)) may be represented by Equation 1 below.

Y = X_D + p-e^J<XX_RS + N_NAWGN ( 1 )

In Equation 1, X_D is the signal for a data symbol received from the destination station 108, p is an amplitude factor, j is the imaginary term, a is a random phase offset between -IJ and H, and N_NAWG_N is a Gaussian noise term.

[0036] The signal Y can be demodulated by first determining an estimate X_D for the signal X_D received from the destination station 108. This estimate may be determined using, for example, a maximum likelihood receiver to determine a minimum distance of the received signal from each of the expected signals for each of the constellation points of the constellation diagram 200 in FIG. 2. Specifically, the decoder may first determine which of the symbols Mo, Mi, M₂ and M3 was sent by the destination station 108 by determining such a minimum distance. The estimate XD may be determined according to Equation 2 below.

Using Equation 2, a maximum likelihood receiver may determine the estimate X_D by determining the minimum of the squares of all possibilities of X_D (the constellation points of the constellation diagram 200) subtracted from the received signal Y.

[0037] Once the estimate XD is made, such as by a maximum likelihood receiver, an estimate X_RS for the signal X_RS received from the relay station 106 can be made. Again, this estimate can be made using a maximum likelihood receiver to determine a minimum distance of the received signal yiess the estimate Xβ for the signal^ from each of the expected signals for each of the constellation points of the constellation diagram 210 in FIG. 2 to determine which of the symbols Ro, Ri, R₂ and R₃ was sent by the relay station 106. The estimate X_RS may be determined using Equation 3 below.

Using Equation 3, a maximum likelihood receiver may determine the estimate X_RS by determining the minimum of the squares of all possibilities of X_RS (the constellation points of the constellation diagram 210) subtracted from the received signal Y minus the estimate X_D from the Equation 3 above.

[0038] Alternatively, the estimates for XD and X_RS may be determined concurrently (e.g., using maximum likelihood receiver) to determine a minimum distance of the received signal Y from expected signals represented by each of the constellation points of the constellation diagram 300 in FIG. 3. Specifically, the signal may be demodulated by comparing the received signal Yto expected signals for each of the 16 constellation points in the constellation diagram 300. The concurrent estimates for X_D and X_RS may be made by a maximum likelihood receiver using Equation 4 below. (XD , XRS ) = min \\Y-X_S (4)

Using Equation 4, a maximum likelihood receiver may determine the estimate X_D and X_RS by determining the minimum of the squares of all possibilities and combinations of X_D and X_RS (the constellation points of the constellation diagram 300 of the combined constellation points of constellation diagrams 200 and 210) subtracted from the received signal Y.

[0039] As was noted above, a plurality of data symbols may be used to represent ACKTNACK messages. For example, because ACK/NACK messages are considered to be very important messages, they may be strongly coded to ensure that they are accurately received. For instance in 802.16 WiMAX systems, ACK/NACK messages are encoded using codewords that include 24 QPSK symbols. ACK/NACK messages are typically a single bit where, for example an positive acknowledgment (ACK) may be represented by a 'O₅' while a negative acknowledgment (NACK) may be represented by a ' 1.' Accordingly, in 802.16 systems, 48 bits (24 QPSK symbols with 2 bits per symbol) are used to encode and transmit ACK/NACK messages, which represents a code rate of 1/48.

[0040] Various techniques may be used for encoding ACK/NACK messages, for instance the ACK/NACK messages may be associated with corresponding codewords in a lookup table. Alternatively, error correction coding could be used to strongly code the ACK/NACK messages. The specific technique used to encode ACK/NACK messages depends on the particular embodiment.

[0041] Any number of techniques may be used to transmit ACK/NACK messages. For instance, the ACK/NACK messages (codewords) may be transmitted in a shared data channel (uplink or downlink) or, alternatively, may be sent in a control channel, depending on the particular embodiment. FIGs. 4 and 5 illustrate an example embodiment that may be used for transmitting ACK/NACK message in an 802.16 WiMAX wireless communication system.

[0042] FIG. 4 is a diagram illustrating an uplink partially used subchannel (UL

PUSC) 400 that may be used for transmitting data symbols of respective codewords for ACK/NACK messages in an 802.16 WiMAX system. In such an approach, data symbols are transmitted using PUSC tiles 410, where each tile includes 12 carriers (4x3). FIG. 5 illustrates a single tile 410. Data may be communicated over the UL PUSC 400 in slots, with each slot including 24 sub-carriers distributed over 3 Orthogonal Frequency Division Multiplexed (OFDM) carriers. In such an approach, the four corner symbols of each tile 410 (shown black in FIGs. 4 and 5) are used for pilot subcarriers (e.g., for synchronization and channel estimation). Accordingly, there are eight symbols per tile (Mo ... M₇) that may be used for communicating data symbols associated with an ACK/NACK message (e.g., codewords). Therefore, each ACK/NACK message may be distributed over three tiles (i.e., 24 QPSK symbols total). [0043] When transmitting ACK/NACK message codewords, a half subchannel of the UL PUSC 400 may be used. A half subchannel may include the odd (1, 3, 5) tiles 410 or the even (0, 2, 4) tiles 410 of the UL PUSC 400. Further, using the hierarchical modulation techniques described above, two ACK/NACK messages (e.g., an ACK/NACK message for the relay station 106 and an ACK/NACK message for the destination station 108 may be sent per half subchannel per slot. Accordingly, four ACK/NACK messages (two per half subchannel) may be sent per subchannel slot, such as relay station ACK/NACK and destination station ACK/NACK messages for sequential packets.

[0044] For each ACK/NACK message sent in the UL PUSC 400, the tiles 410 may be used to communicate the data symbols of a corresponding ACK/NACK codeword in accordance with the constellation diagram 500 shown in FIG. 5. The amplitude of the data symbols PO, Pl, P2 and P3 may vary in accordance with a hierarchical modulation scheme, such as previously described. For example, an amplitude factor may be applied for data symbols sent from relay stations as compared to data symbols sent from user equipment (destination stations) or access points (source stations, which may function as a destination station in an uplink data transmission). Again, two data symbols may be transmitted substantially simultaneously for each of the data symbols M₀ ... M₇ of each tile 410.

[0045] As previously described, ACK/NACK messages may be represented by codewords that each include 24 QPSK symbols. These codes words may be based on a vector index table, such as the vector index table 600 illustrated in FIG. 6. Each of the vector indices in the table 600 is associated with a series of data symbols in a single tile 410. The data symbols in the table 600 are represented using the data symbol designators PO, Pl, P2 and P3 from the constellation diagram 500 in FIG. 5. These designations are used merely for purpose of illustration. As discussed above with respect to FIG. 2, the arrangement of the two data bits associated with each of the data symbols PO, Pl, P2 and P3 may vary depending on the particular embodiment.

[0046] The vector indices in the table 600 are associated with sequences of the data symbols PO, Pl, P2 and P3 used for each of the data symbols M₀ ... M₇ in a given PUSC tile 410. For instance, vector index 0 is associated with the data symbol sequence PO, Pl, P2, P3, PO, Pl, P2, P3.

[0047] The vector indices shown in the table 600 may be used to construct codewords for ACK/NACK messages. For example, three vector indices may be selected to form a codeword, as three vector indices represent three tiles 410 of data symbols, or the 24 total QPSK data symbols of a codeword in this example embodiment. Further, the vector indices shown in the table 600 are merely illustrative and other vector indices may be used. The particular indices shown in FIG. 6 are illustrated as they may allow for constructing codewords for ACK/NACK messages that reduce the likelihood of error when sending ACK/NACK messages using hierarchical modulation. Alternatively, vector indices that allow for constructing orthogonal codewords may be used.

[0048] By demodulating (hierarchically modulated) signals that include two data symbols per each of the data symbol locations in the tiles 410 for a half subchannel, the data symbol sequences for each tile may be determined and then compared to the table 600 (which may function as a lookup table). Accordingly, the table 600 may be used to determine the respective vector indices (i.e., three indices) for each of two code words included in the three tiles (e.g., a relay station ACK/NACK codeword and a destination station ACK/NACK codeword).

[0049] Once the vector indices are determined for each of the codewords, the vector index sequences may be compared with corresponding lookup tables to determine corresponding ACK/NACK messages. FIG. 7 illustrates a lookup table 700 for decoding destination ACK/NACK codewords. As shown in the table 700, a vector index sequence of 0, 0. 0 indicates that the destination station 108 sent an ACK message. The table 700 also illustrates that a vector index sequence of 2, 3, 1 indicates that the destination station 108 sent a NACK message. FIG. 8 illustrates a lookup table 800 for decoding relay station ACK/NACK messages. As shown in the table 800, a vector index sequence of 0, 0, 0 (as with the table 700) indicates that the relay station 106 sent an ACK message. As also shown in table 800, a vector sequence 4, 5, 6 indicates that the destination station 106 sent a NACK message. As indicated above, the vector sequences shown in tables 700 and 800 were selected (based on empirical studies and simulation) to reduce the likelihood of signal interference when simultaneously communicating the ACK/NACK message codewords using hierarchical modulation. As an alternative, vector indices that result in the ACK/NACK messages being orthogonal may also be used to reduce the likelihood of interference and possible errors when demodulating and decoding the codewords.

[0050] FIG. 9 is a flow chart illustrating an example embodiment of a method 900 for data communication in a wireless network. FIG. 9 will be described with further reference to FIG. 1.

[0051] The method 900 may include, at block 902, sending a data packet to both a relay station 106 and a destination station 108 in the wireless network 102. The data packet may be communicated to the relay station 106 and the destination station 108 in a substantially simultaneous fashion. As discussed above, the packet may include a control message that assigns an ACK/NACK frame for the relay station 106 and the destination station 108 to communicate their ACK/NACK message codewords.

[0052] The method 900 may further include, at block 904, receiving a combined signal, where the combined signal includes a first sub-signal and a second sub-signal, which may be received substantially simultaneously in the assigned ACK/NACK frame (e.g., via a half subchannel of an UL PUSC). In the method 900, the first sub-signal may include one of a relay station acknowledgment (ACK) and a relay station negative acknowledgment (NACK) for the data packet. As previously described, the ACK/NACK message from the relay station 106 may be encoded in a codeword, such as a codeword including 24 QPSK data symbols. The second sub-signal may include one of a destination station acknowledgment (ACK) and a destination station negative acknowledgment (NACK) for the data packet. In like fashion as the first sub-signal, the ACK/NACK message from the destination station 108 may be encoded in a codeword.

[0053] The method 900 may also include, at block 906, demodulating the combined signal using hierarchical modulation to determine whether the relay station sent the relay station ACK or the relay station NACK, or an associated codeword representing the relay station ACK/NACK message. Also, the demodulation at block 906 may include determining whether the destination station sent the destination station ACK or the destination station NACK, or an associated codeword representing the destination station ACK/NACK message. [0054] The method 900 may still further include, at block 908, decoding the codeword representing the relay station ACK/NACK message to determine whether the relay station 106 sent an ACK or a NACK. At block 910, the method 900 may further include decoding the codeword representing the destination station ACK/NACK message to determine whether the destination station 108 sent an ACK or a NACK. As previously discussed, the codewords may be decoded using a lookup table or, alternatively using error correction codes, as two examples.

[0055] FIG. 10 is a block diagram showing an apparatus according to an example embodiment. The apparatus 1000, which may include a source station 104, relay station 106, or destination station 108 according to example embodiments, may include a wireless transceiver 1002 (or wireless interface), a controller (or processor) 1004, and a memory 1006. The transceiver 1002 may include a wireless transmitter for transmitting radio frequency signals. The wireless transceiver 1002 may also include a wireless receiver for receiving wireless signals.

[0056] The memory 1006 may be configured to store a packet, such as a data packet in accordance with any number of data transport protocols, for example. The controller 1004 may perform any number of the operations described herein, such as demodulating a relay station ACK or a relay station NACK and a destination station ACK or a destination station NACK. The wireless transceiver 1002 may be configured to send the packet to the relay station 106 and the destination station 1008, and to receive the relay station ACK or the relay station NACK and the destination station ACK or the destination station NACK, according to an example embodiment. The wireless transceiver 1002 may include a single component with both transmission and reception capabilities, or a separate transmitter and receiver, according to example embodiments.

[0057] The controller 1004 may be configured to perform any number operations descried herein. For example, the controller 1004 may be configured to operate as a maximum likelihood receiver that may demodulate (e.g., using the hierarchical demodulation techniques discussed above) a combined signal to determine each data symbol of a first set of data symbols corresponding with a relay station ACK or NACK and each data symbol of a second set of data symbols corresponding with a destination station ACK or NACK. The controller 1004 may be further configured to determine, e.g., by decoding the first set of data symbols and the second set of data symbols, whether the relay station sent the relay station ACK or the relay station NACK and whether the destination station sent the destination station ACK or the destination station NACK.

[0058] Implementations of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Implementations may implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[0059] Method steps may be performed by one or more programmable processors executing a computer program to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[0060] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in special purpose logic circuitry.

[0061] To provide for interaction with a user, implementations may be implemented on a computer having a display device, e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0062] Implementations may be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation, or any combination of such back-end, middleware, or front-end components. Components may be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (LAN) and a wide area network (WAN), e.g., the Internet.

[0063] While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments of the invention.

Claims

WHAT IS CLAIMED IS:

1. A method for data communication in a wireless network, the method comprising: receiving a signal, the received signal including: a first sub-signal from a first source, the first sub-signal including a first codeword representing a first message, the first codeword including a first plurality of data symbols; a second sub-signal from a second source, the second sub-signal including a second codeword representing a second message, the second codeword including a second plurality of data symbols, wherein the second sub-signal is received substantially simultaneously with the first sub-signal; demodulating the received signal using hierarchical modulation to determine the first codeword and the second codeword by determining, respectively, the first plurality of data symbols and the second plurality of data symbols; decoding the first codeword to determine the first message; and decoding the second codeword to determine the second message.

2. The method of claim 1, wherein: the first plurality of data symbols includes a first plurality of QPSK symbols of a first amplitude; and the second plurality of data symbols includes a second plurality of QPSK symbols of a second amplitude.

3. The method of claim 1, wherein: the first source is a destination station; the first message includes a destination station acknowledgment (ACK) or negative acknowledgment (NACK) from the destination station, the destination station ACK or NACK respectively acknowledging or negatively acknowledging successful receipt of a data packet by the destination station; the second source is a relay station; and the second message includes a relay station ACK or NACK from the relay station, the relay station ACK or NACK respectively acknowledging or negatively acknowledging successful receipt of the data packet by the relay station.

4. The method of claim 3, further comprising substantially simultaneously transmitting a data packet to the first source and the second source, wherein the first sub- signal and the second sub-signal are received in response to transmission of the data packet.

5. The method of claim 1, wherein the first sub-signal and the second sub- signal are modulated in accordance with a common modulation scheme.

6. The method of claim 1, wherein: the first sub-signal is modulated in accordance with a first modulation scheme; and the second sub-signal is modulated in accordance with a second modulation scheme, the second modulation scheme being different than the first modulation scheme.

7. The method of claim 1, wherein demodulating the received signal comprises: estimating the first sub-signal from the received signal; and estimating the second sub-signal from the received signal and the estimate of the first sub-signal.

8. The method of claim 1, wherein demodulating the received signal comprises concurrently estimating the first sub-signal and the second sub-signal from the received signal.

9. The method of claim 1, wherein decoding the first codeword to determine the first message and decoding the second codeword to determine the second message comprises decoding the first and second codewords using a look up table.

10. The method of claim 1, wherein decoding the first codeword to determine the first message and decoding the second codeword to determine the second message comprises decoding the first and second codewords using error correction codes.

1 1. A method for data communication in a wireless network, the method comprising: sending a data packet to both a relay station and a destination station in the wireless network; receiving a combined signal, the combined signal including: a first sub-signal from the relay station, the first sub-signal including one of a relay station acknowledgment (ACK) and a relay station negative acknowledgment (NACK) for the data packet, wherein: the first sub-signal is received during an ACK/NACK frame corresponding with the data packet; the relay station ACK acknowledges successful receipt of the data packet by the relay station; and the relay station NACK acknowledges unsuccessful receipt of the data packet by the relay station; a second sub-signal from the destination station, the second sub-signal including one of a destination station acknowledgment (ACK) and a destination station negative acknowledgment (NACK) for the data packet, wherein: the second sub-signal is also received during the ACK/NACK frame corresponding with the data packet and is received substantially simultaneously with the first sub-signal; the destination station ACK acknowledges successful receipt of the data packet by the destination station; and the destination station NACK acknowledges unsuccessful receipt of the data packet by the destination station; demodulating the combined signal using hierarchical modulation to determine: whether the relay station sent the relay station ACK or the relay station NACK; and whether the destination station sent the destination station ACK or the destination station NACK.

12. The method of claim 11, wherein sending the data packet includes sending a control message assigning the ACK/NACK frame to both the relay station and the destination station for substantially simultaneously transmitting, respectively, the first sub-signal and the second sub-signal.

13. The method of claim 12, wherein assigning the ACK/NACK frame includes assigning an odd-half of an Uplink Partially Used Subchannel (UL PUSC) or an even-half of the UL PUSC.

14. The method of claim 1 1, wherein the first sub-signal and the second sub- signal are substantially simultaneously received via a common half of an Uplink Partially Used Subchannel (UL PUSC) during the ACK/NACK frame.

15. The method of claim 1 1, wherein : the received relay station ACK or the received relay station NACK includes a first codeword including a first set of 24 QPSK data symbols; and the received destination station ACK or the received destination station NACK includes a second codeword including a second set of 24 QPSK data symbols.

16. The method of claim 1 1, wherein: the destination station NACK and the relay station NACK include a first sequence of data symbols; the destination station ACK includes a second sequence of data symbols; and the relay station ACK includes a third sequence of data symbols, wherein the first, second and third set of data symbols are unique with respect to one another.

17. The method of claim 1 1, wherein: the relay station ACK or the relay station NACK is received via a first set of Uplink Partially Used Subchannel (UL PUSC) Tiles in an UL PUSC during the ACK/NACK frame; and the destination station ACK or the destination station NACK is received via a corresponding second set of UL PUSC Tiles in the UL PUSC during the ACK/NACK frame.

18. The method of claim 1 1, wherein demodulating the combined signal comprises: estimating the first sub-signal from the combined signal; and estimating the second sub-signal from the combined signal and the estimate of the first sub-signal.

19. The method of claim 1 1, wherein demodulating the combined signal comprises concurrently estimating the first sub-signal and the second sub-signal from the combined signal.

20. The method of claim 1 1, wherein: the first sub-signal includes a first codeword, the first codeword: representing the relay station ACK or the relay station NACK; and including a first plurality of data symbols; and the second sub-signal includes a second codeword, the second codeword: representing the destination station ACK or the destination station NACK; and including a second plurality of data symbols.

21. The method of claim 20, further comprising: decoding the first codeword using a lookup table to determine whether the relay station sent the relay station ACK or the relay station NACK; and decoding the second codeword using a lookup table to determine whether the destination station sent the destination station ACK or the destination station NACK.

22. The method of claim 20, further comprising: decoding the first codeword using error correction codes to determine whether the relay station sent the relay station ACK or the relay station NACK; and decoding the second codeword using error correction codes to determine whether the destination station sent the destination station ACK or the destination station NACK.

23. An apparatus comprising: a memory configured to store a packet; a wireless transceiver configured to: send the packet to a relay station and a destination station; receive a combined signal, the combined signal including: a first sub-signal from the relay station, the first sub-signal including one of a relay station acknowledgment (ACK) and a relay station negative acknowledgment (NACK) for the data packet, wherein: the first sub-signal is received during an ACK/NACK frame corresponding with the data packet; the relay station ACK acknowledges successful receipt of the data packet by the relay station; and the relay station NACK acknowledges unsuccessful receipt of the data packet by the relay station; a second sub-signal from the destination station, the second sub- signal including one of a destination station acknowledgment (ACK) and a destination station negative acknowledgment (NACK) for the data packet, wherein: the second sub-signal is also received during the ACK/NACK frame corresponding with the data packet and is received substantially simultaneously with the first sub-signal; the destination station ACK acknowledges successful receipt of the data packet by the destination station; and the destination station NACK acknowledges unsuccessful receipt of the data packet by the destination station; and a processor configured to: demodulate the combined signal using hierarchical modulation to determine: whether the relay station sent the relay station ACK or the relay station NACK; and whether the destination station sent the destination station ACK or the destination station NACK.