Abstract:
In a wireless communication system, data is encoded by packet indifferent (PI) coding and some packets are transmitted omnidirectionally while supplemental packets are transmitted directionally to a user with a poor air link. PI encoding is defined herein as encoding in which the source data can be recovered from any K of the encoded packets, regardless of which of the encoded packets are received, where K=N+A. N is equal to the number of packets in the source data and A is the number of additional packets required due to the PI encoding. A subset of M data packets can be sent to one or many users from an omnidirectional antenna, where M is greater than or equal to K. If less than K data packets are received by at least one user, then the data block is not successfully received by that user. A number R of supplemental packets can be sent to users that did not receive K data packets successfully. The supplemental packets can be sent by a directional antenna to the specific user or users that did not receive K data packets.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates generally to wireless communication and more particularly to systems and methods for coding and transmitting wireless communications signals.  
       BACKGROUND OF THE INVENTION  
       [0002]     Consumers are increasingly demanding data services on mobile wireless communication devices, such as cell phones. For example, streaming video is a fun and useful new application for cell phones. One application of streaming video is broadcast video. Broadcast means that data is sent to many users simultaneously. For example, a video movie may be broadcast from a cellular base station to many cell phone users.  
         [0003]     One problem with streaming video applications and other similar applications is that they require much more bandwidth than traditional voice calls. The increased bandwidth requirements tend to overload network resources. Additionally, different users have different air link conditions. A user with poor coverage may not successfully receive and decode as much of the data sent as some other users within the same broadcast area.  
         [0004]     The user with poor channel conditions may be known in advance or not known in advance.  
       SUMMARY OF THE INVENTION  
       [0005]     In order to overcome the problems associated with conventional approaches for transmitting data in wireless communication networks, the data is encoded by packet indifferent (PI) coding and some packets are transmitted omnidirectionally while supplemental packets are transmitted directionally to a user with a poor air link. PI encoding is defined herein as encoding in which the source data can be recovered from K of the encoded packets, regardless of which of the encoded packets are received, where K=N+A. N is equal to the number of packets in the source data, and A is the minimum number of additional packets required due to the PI encoding. Thus, PI encoding applies to rateless or fountain codes and Reed-Solomon codes, which are described in U.S. patent application Ser. No. 11/125,517, filed on May 9, 2005, which is hereby incorporated by reference.  
         [0006]     A subset of M=K+L data packets can be sent to one or many users from an omnidirectional antenna. L is a predicted number of lost packets. If K data packets are received, then the data block is successfully received. If less than K data packets are received by at least one user, then the data block is not successfully received by that user. A number R of supplemental packets can be sent to users that did not receive K data packets successfully. The R supplemental packets can be sent by a directional antenna to the specific user or users that did not receive K data packets.  
         [0007]     The sending of supplemental packets by the directional antenna may or may not consume system resources as much as would be consumed if the supplemental packets were sent by the omnidirectional antenna. Thus, even users with poor coverage conditions can receive a sufficient number of packets to reconstruct the original data, and this can be accomplished without burdening the entire set of users.  
         [0008]     In the case where the user or location is known in advance, the supplemental data packets may be sent simultaneous with the broadcast packets or later. In the case where the user or location is not known in advance, there are two possibilities. In the first possibility, the system waits until at least one user reports failure of some of the packets (or fails to report success of all of the packets). Then the system initiates sending the supplemental packets to that user or users. In the second possibility, the system uses one or more directional beams sweeping around the cell area sending the supplemental data packets in the same timeframe as the broadcast packets.  
         [0009]     More or less supplemental packets can be sent to the user or location with a poor air link depending on how many of the broadcast packets the user with a poor air link was able to receive or was predicted to receive or both.  
         [0010]     Other aspects, advantages, and novel features of the invention will become apparent from the following Detailed Description of Preferred Embodiments, when considered in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Preferred embodiments of the present inventions taught herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which:  
         [0012]      FIG. 1  is a block diagram illustrating a wireless communication system in which a data block is transmitted omnidirectionally and adaptively directionally.  
         [0013]      FIG. 2  is a block diagram illustrating a wireless communication system in which a data block is transmitted omnidirectionally and rotatingly directionally.  
         [0014]      FIG. 3  is a block diagram illustrating a wireless communication system in which a data block is transmitted omnidirectionally and fixedly directionally.  
         [0015]      FIG. 4  is a call flow diagram illustrating a wireless communication system call flow in which a data block is transmitted omnidirectionally and directionally.  
         [0016]      FIG. 5  is a block diagram illustrating a wireless communication system in which a data block is transmitted omnidirectionally and directionally. 
     
    
     DETAILED DESCRIPTION  
       [0017]      FIG. 1  is a block diagram illustrating a wireless communication system in which a data block is transmitted omnidirectionally and adaptively directionally. Access node controller (ANC)  15  is connected to the internet (not shown) and a private network such as a wireless communication service provider network (not shown) of which ANC  15  may be a part. Data blocks such as video frames are received by ANC  15  at input  17  from the internet and/or the aforementioned private network. For example, a wireless communication service provider may be broadcasting a movie. The movie video frames are received at input  17 . As another example, the wireless communication service provider may be broadcasting movie trailers or other video material. As still another example, the data received at input  17  may be video for video teleconferencing.  
         [0018]     The data block is received in packet processor and mulitplexer (PPM)  19 . PPM  19  may be similar to the PPM described with respect  FIG. 5  of the above referenced U.S. patent application Ser. No. 11/125,517. PPM  19  optionally encodes the data block by PI encoding.  
         [0019]     ANC  15  is connected to Access Node  1  (AN 1 )  25  and Access Node  2  (AN 2 )  30 . AN 1   25  is any type of omnidirectional wireless access node. For example, AN 1   25  may be a base station (access node) compliant with the code division multiple access (CDMA) standards known as TIA/EIA IS-2000 and/or TIA-856 (1×EV-DO) or with GSM, wideband CDMA (W-CDMA), or any other convenient wireless communication system that is capable of omnidirectional transmission. In fact, it may be possible that in the future, communication systems will be configurable from omnidirectional to directional. In that case, AN 1   25  would be omnidirectional if AN 1   25  was configured at the time to be omnidirectional. Omnidirectional could mean covering all directions within a sector. The coverage areas of cellular base stations are commonly divided into three sectors, each sector including approximately 120 degrees azimuthally from the base station. AN 1   25  could actually refer to a base station transmitting in a sector.  
         [0020]     AN 2   30  is a directional base station. For example, AN 2   30  might be a base station with the antenna or antennas configured to transmit a narrow beam in the direction of a certain building  32 . AN 2   30  might be compliant with the standard known as IEEE 802.16 (also referred to as “WiMAX”). A version of WiMAX is expected to be useful for fixed, line-of-sight communications. Thus, WiMAX may be used to enhance the wireless data throughput to a building, such as building  32 .  
         [0021]     Regarding omnidirectional transmission, it should be understood that purely uniform transmission power in all directions is the ideal case, but variations from the ideal are within the definition of omnidirectional. Directional is defined herein to mean any directionality other than omnidirectional. A single narrow beam pointing from a transmitter to a receiver is the ideal case of directional transmission, but various beam shapes and multiple beams are considered directional transmissions.  
         [0022]     PPM  19  encodes data block by PI encoding. Since data block is encoded by PI encoding it does not matter which of the encoded packets are received as long as at least K packets are received. Further, it does not even matter whether the packets are received from the same transmitter or even over the same network. Advantageously, a receiver, such as a wireless handset, can receive some packets from AN 1   25  and some packets from AN 2   30  as long as the handset is able to decode/demodulate packets from AN 1   25  and AN 2   30 . The handset can combine the packets received from AN 1   25  with the packets received from AN 2   30  to reconstruct the source data block. Thus, a handset inside building  32 , for example, can receive some packets from a first subset of packets sent over AN 1   25  and some packets from a second subset of packets sent over AN 2   30 . The handset can combine the packets from the first and second subsets to reconstruct the source data block.  
         [0023]     For example, a first subset of the PI encoded data packets may be broadcast over AN 1   25 . The first subset may include enough PI encoded data packets for a user who received all or nearly all of them (e.g., 98% of them) to reconstruct the source data block. For example, AN 1   25  may be an IS-2000 compliant access node. Some users might not successfully receive and decode enough of the packets in order to reconstruct the source data block.  
         [0024]     For example, a receiver inside building  32  might have poor reception due to attenuation or the multipath environment of the signal in building  32 . To Building  32  might be equipped with a WiMAX receiver shown as antenna  34 . Thus, packets can be routed through directional antenna  36  connected to AN 2   30 , which may be a WiMAX base station. Packets can be sent from AN 2   30  to WiMAX receiver  34 . The packets can be retransmitted inside building  32  by, for example, a wireless local area network (WLAN) (not shown), such as, for example, IEEE 802.11, known as Wi-Fi. Then a particular receiver inside building  32  can receive some packets directly from AN 1   25  and some packets from AN 2   30  through antenna  34  and retransmission through WLAN (not shown) inside building  32 .  
         [0025]     Alternatively, instead of a fixed directional antenna  36 , the supplemental packets can be transmitted by an adaptive directional antenna, as shown with respect to  FIG. 2 . The system shown with respect to  FIG. 2  is similar to the system shown with respect to  FIG. 1 , except that in  FIG. 2 , ANC  15  is connected to an adaptive directional AN  3  (AN 3 )  40 . AN 3   40  has an adaptive directional antenna or antenna array  42 . Adaptive directional antennas are described in U.S. Pat. No. 6,865,377, issued Mar. 8, 2005, U.S. Pat. No. 6,828,923, issued Dec. 7, 2004, and U.S. Pat. No. 6,888,505, issued May 3, 2005, which are incorporated herein by reference.  
         [0026]     Adaptive directional antenna array  42  is used to transmit and steer a signal beam  44  to follow a mobile wireless communication device  46 , also referred to as mobile station (MS)  46 . Advantageously, MS  46  can receive some packets from omnidirectional AN 1   25  and some packets from adaptive directional AN 3   40 . MS  46  can reconstruct source data block from packets received from either AN 1   25  or AN 3   40 .  
         [0027]     Referring to  FIG. 3 , in yet another alternative, ANC  15  may be connected to AN  4  (AN 4 )  50 . AN 4   50  is used to transmit the supplemental packets in a rotating directional pattern  53 . That is, AN 4   50  has a directional antenna  56 , but instead of transmitting in a known direction of MS  46 , AN 4   50  transmits the supplemental packets essentially in all directions by rotating beam  53  around AN 4   50 . In one embodiment, beam  53  is rotated azimuthally around AN 4   50 , as shown by arrow  59 .  
         [0028]      FIGS. 1-3  are shown as separate figures, but, in fact, it is possible that the same system could operate in each of the three methods that are illustrated by  FIGS. 1-3 . That is, AN 2   30 , AN 3   40  and AN 4   50  may actually be the same AN. More specifically, a single AN may be used to transmit in a fixed directional manner as shown with respect to  FIG. 1 , an adaptive directional manner as shown with respect to  FIG. 2  and a rotating directional manner as shown with respect to,  FIG. 3 . AN 2   30 , AN 3   40  and AN 4   50  could be collocated with AN 1   25 .  
         [0029]      FIG. 4  is a call flow diagram illustrating a wireless communication system call flow in which a data block is transmitted omnidirectionally and directionally. The call flow diagram is applicable to each of the systems or methods illustrated with respect to  FIGS. 1-3 . Referring to  FIG. 4 , four entities are shown: MS  46 , AN 1   25 , ANC  15  and AN 2   30 . As described above, AN 3   40  and AN 4   50  are interchangeable with AN 2   30  in  FIG. 4  (and also in  FIG. 5 , described below). The call flow starts at signal  65 , in which ANC  15  sends a first subset of the PI encoded data packets to AN 1   25  for omnidirectional transmission. The omnidirectional transmission could be broadcast or unicast. AN 1   25  responds by sending the first subset of the PI encoded data packets to MS  46  omnidirectionally, in communication  70 .  
         [0030]     If MS  46  successfully received and decoded sufficient packets to reconstruct the source data block, then in signal  75 , MS  46  sends an acknowledgement message (ACK), or does not send a Non-acknowledgement message (NACK), depending on whether the communication system is an ACK or NACK system, to AN 1   25 . In that case, MS  46  does not need to receive any of the second subset of PI encoded packets. Note that signal  75  may actually be the absence of a signal, but the absence of an ACK is interpreted as failure to receive and decode enough packets.  
         [0031]     If MS  46  did not successfully receive and decode enough of the packets to reconstruct the source data block, then in signal  75 , MS  46  does not send an ACK (or sends a NACK, depending on whether the communication system is an ACK or NACK system) to AN 1   25 . In that case, MS  46  needs more packets (that is, at least some of the second subset) in order to reconstruct the source data block. Note again that signal  75  may actually be the absence of a signal, but the absence of a NACK is interpreted as success in receiving and decoding sufficient of the packets.  
         [0032]     Considering the case where no ACK is sent or a NACK is sent in signal  75 , then in signal  80 , AN 1   25  forwards the NACK or does not send an ACK to ANC  15  in signal  80 . At this point, ANC  15  knows that MS  46  was unable to receive and decode sufficient of the PI encoded packets. Responding to this information, ANC  15  sends a second subset of PI encoded packets to AN 2   30  for directional transmission to MS  46  in signal  85 . In signal  90 , AN 2   30  transmits the second subset of PI encoded packets to MS  46  in a directional transmission. As referenced above, the directional transmission of signal  90  could be at least in any of the forms illustrated in  FIGS. 1-3 .  
         [0033]     The above discussion refers to communication systems using ACK or NACK messages. However, the ideas described herein could be applicable to a communication system without ACK or NACK messages. Sending supplemental coded packets to known regions with poor coverage without ACK or NAKC would increase the likelihood of successful data block retrieval without making significant change to an existing system without ACK or NACK, such as, for example, broadcast systems. Some broadcast services lack ACK or NACK. This could be a fill for the known coverage hole or to accommodate an area that needs more coverage at a certain time, for example, a stadium such as a ballpark with known heavy usage periods such as game times.  
         [0034]      FIG. 5  is a block diagram illustrating a wireless communication system in which a data block is transmitted omnidirectionally and directionally. Specifically,  FIG. 5  highlights certain aspects of ANC  15 . Source data blocks are received at input  17 . An initial decision is made regarding whether the source data is a candidate for transmission both omnidirectionally and directionally. The initial decision is made by scheduler  21  in conjunction with other components or modules not shown, such as, for example, classifier, quality of service module and channel state indicator module. QoS module, classifier and CIS module are shown and described in the previously referenced U.S. patent application Ser. No. 11/125,517, and will not be described here further.  
         [0035]     The decision is based on inputs such as whether omnidirectional and directional transmissions sources (e.g., AN 1   25  and AN 2   30 , respectively) are available for transmission to MS  46 . If scheduler  21  decides that the source data block should be transmitted only omnidirectionally, then scheduler- 21  causes PI encoder and multiplexer  108  to route all coded packets from the source data block to AN 1   25 . All packets are encoded using PI and transmitted by AN 1   25 . If, however, scheduler  21  determines that source data block is a candidate for omnidirectional and directional transmission, then scheduler  21  causes PI encoder and multiplexer  108  to route PI encoded packets to both AN 1   25  and AN 2   30 .  
         [0036]     Scheduler  21  schedules a number M of PI encoded packets for transmission via AN 1   25 . Scheduler  21  causes PI encoder and multiplexer  108  to send the first subset of PI encoded packets to AN 1   25 , as shown by signal  65  (described above with respect to  FIG. 4 ). When ANC  15  receives NACK or no ACK signal  80 , signal  80  is sent to scheduler  21 . It is noted that in a no-feedback system, signal  80  is not used, and in this case, Scheduler  21  can decide a-priori that some of the packets are sent on AN 1   25  and some are sent on AN 2   30 .  
         [0037]     Scheduler  21  responds to signal  80 , by determining that a number R of supplemental PI encoded data packets should be sent directionally from AN 2   30  to MS  46 . Scheduler  21  causes PI encoder and multiplexer  108  to send the R supplemental PI encoded data packets to AN 2   30 , as shown by signal  85 . As stated above, AN 2   30  in  FIG. 5 , may be AN 3   40  or AN 4   50 . AN 2   25  transmits the second subset of PI encoded data packets to MS  46 , as shown by signal  90 .  
         [0038]     The number R may be estimated directly from the number of NACK&#39;s or ACK&#39;s signals received from MS  46 . For example, if MS  46  fails to send an ACK signal for six of the M data packets, then the number R may be six, or some number proportional to six. Alternatively, the number R may be estimated based on signal quality indicators received from MS  46 . For example, if the communication system used by AN 1   25  and MS  46  is an IS-2000 system and MS  46 , has indicated to AN 1   25  that MS&#39;s  46  frame error rate is high, then the number R will be estimated higher to account for MS&#39;s  46  high frame error rate. Methods for calculating an appropriate number R of supplemental PI encoded packets based on frame error rate are well known and will not be discussed here further, in the interest of brevity. Advantageously, MS  46  can receive packets from either AN 1   25 , or AN 2   30  and use the packets from either AN to reconstruct the source block of data.  
         [0039]     Further, while embodiments and implementations of the invention have been shown and described, it should be apparent that many more embodiments and implementations are within the scope of the invention. Accordingly, the invention is not to be restricted, except in light of the claims and their equivalents.