Abstract
A broadcast/multicast transmission format includes a data portion and a cyclic prefix (CP) coupled to the traffic data portion. A method and system for providing broadcast/multicast transmissions with the application to communication systems that perform broadcast or multicast transmission is also disclosed. The addition of a pilot to the data portion of the transmissions is also disclosed.
Claims
1-32. (canceled)
33. A method, comprising: receiving a broadcast/multicast transmission; extracting data fields from the received transmission; extracting a pilot signal from the data fields; performing channel estimation using the extracted pilot signal; and removing any cyclic prefix (CP) associated with the data fields.
34. A method as defined in claim 33, wherein the data fields each comprise a cyclic prefix appended to a data portion.
35. A method as defined in claim 33, wherein the data fields each comprise a cyclic prefix pre-pended to a data portion.
36. A method as defined in claim 34, wherein the data fields each comprise a cyclic prefix pre-pended to the data portion.
37. A method as defined in claim 33, wherein the data Melds each comprise a pilot symbol appended to a data portion.
38. A method as defined in claim 33, wherein the data fields each comprise a cyclic prefix pre-pended to a data portion.
39. A method as defined in claim 34, wherein the data fields each comprise a cyclic prefix pre-pended to the data portion.
40. A method as defined in claim 33, wherein the data fields in the received broadcast/multicast transmission were not transmitted using cell/sector specific long code spreading.
41. A method as defined in claim 33, wherein the data fields in the received broadcast/multicast transmission were transmitted using content-dependent long code spreading.
42. An apparatus, comprising: means for receiving a broadcast/multicast transmission; means for extracting data fields from the received transmission; means for extracting a pilot signal from the data fields; means for performing channel estimation using the extracted pilot signal; and means for removing any cyclic prefix (CP) associated with the data fields.
43. An apparatus, comprising: circuitry configured to receive a broadcast/multicast transmission; circuitry configured to extract data fields from the received transmission; circuitry configured to extract a pilot signal from the data fields; circuitry configured to perform channel estimation using the extracted pilot signal; and circuitry configured to remove any cyclic prefix (CP) associated with the data fields.
44. The apparatus of claim 43, wherein the data fields each comprise a cyclic prefix appended to a data portion.
45. The apparatus of claim 43, wherein the data fields each comprise a cyclic prefix prepended to a data portion.
46. The apparatus of 44, wherein the data fields each comprise a cyclic prefix pre-pended to the data portion.
47. The apparatus of claim 43, wherein the data fields each comprise a pilot symbol appended to a data portion.
48. The apparatus of claim 43, wherein the data fields each comprise a cyclic prefix pre-pended to a data portion.
49. The apparatus of claim 43, wherein the data fields each comprise a cyclic prefix pre-pended to the data portion.
50. The apparatus of claim 43, wherein the data fields in the received broadcast/multicast transmission were not transmitted using cell/sector specific long code spreading.
51. The apparatus of claim 43, wherein the data fields in the received broadcast/multicast transmission were transmitted using content-dependent long code spreading.
52. The apparatus of claim 43 wherein code division multiple access (CDMA) is used to implement a non-data portion of the received broadcast/multicast transmission and orthogonal frequency division access (OFDM) is used to implement a data portion of the received broadcast/multicast transmission.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a drawing highlighting a structure of a prior art channel for an enhanced broadcast/multicast mode (EBM) for HRPD.
[0011] FIG. 2 shows a prior art diagram of a HRPD transmission format;
[0012] FIG. 3 shows a CDMA-CP based broadcast/multicast transmission format in accordance with an embodiment of the invention;
[0013] FIG. 4 shows a cyclic prefix placement in accordance with an embodiment of the invention;
[0014] FIG. 5 shows another cyclic prefix placement in accordance with another embodiment of the invention;
[0015] FIG. 6 shows a block diagram of a receiver in accordance with an embodiment of the invention;
[0016] FIG. 7 shows a communication system in accordance with an embodiment of the invention.
[0017] FIG. 8 shows a transmission format in accordance with another embodiment of the invention.
[0018] FIG. 9 shows another transmission format in accordance with another embodiment of the invention,
[0019] FIG. 10 shows a transmission format in accordance with another embodiment of the invention.
[0020] FIG. 11 shows a flowchart highlighting the reception of a broadcast/multicast transmission in accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] In this description, we use an HRPD system to illustrate one embodiment of the broadcast multicast mode of the present invention. Note that the mode is applicable to any wireless standard and is not limited to HRPD systems.
[0022] In FIG. 3, there is shown a transmission format for the transmission of broadcast/multicast data that is relevant to HRPD as well as to other broadcast/multicast communication systems. The disclosed approach efficiently combines the signals received from the different sectors/cells in a communication system. In accordance with an embodiment of the invention, whenever identical broadcast/multicast data is being transmitted from different sectors/cells in a system, the present invention inserts a cyclic prefix (CP) to the broadcast/multicast data. The CP can be appended, pre-pended or added to both sides of the data. Any cell/sector specific long code spreading is removed for this portion of the transmission in one embodiment of the invention. Alternatively, when identical broadcast/multicast content is transmitted from different sectors/cells in the communication system, a content-dependent long code spreading can be used to differentiate the data from other contents. In the illustrative format shown in FIG. 3, the CP is added to the front and the back of the traffic data 302, 310, 312 and 320. The format also includes the MAC 304, 314, the Pilot 306, 316, and MAC 308,318. As shown in FIG. 3, in accordance with one aspect of the invention, the traffic data portions 302, 312 and 320 include CPs that are added to the front and back of the traffic data that does not use long code spreading. By appending one or more CPs to the traffic packets 302, 310 and 320 the communication system can maintain backward compatibility with the current HRPD system, while allowing for efficient combining of the same signals being received from the different sectors/cells in the system.
[0023] In accordance with an embodiment of the invention, whenever identical broadcast/multicast data is being transmitted from different sectors/cells in a system, a CP is attached to the broadcast/multicast data, as shown in FIG. 3, the CPs can be pre-pended and appended to the data, or as shown in FIG. 4 the CP 404 can be appended to the data 402 only, or as shown in FIG. 5, the CP 502 can be pre-pended to the data 504. One other thing that is done is to remove any long code spreading during transmission of the CP and traffic data.
[0024] Some advantages of using what will be referred to as a CDMA+CP based transmission as shown in FIG. 3 in accordance with an embodiment of the invention is that the CDMA+CP scheme facilitates optimum combining and equalization at the receiver. That is, combining and equalization of the composite long channel from all the sectors transmitting the same content can be done efficiently and with relatively low complexity using a receiver architecture such as that shown in FIG. 6 and which will be discussed further below. The use of the CDMA+CP approach described also provides for backwards compatibility with the current HRPD and other types of broadcast multicast systems since the transmitters sill employ CDMA transmissions. The cell/sector specific long code spreading can be removed from the transmitter as the additional block(s) of CP has to be added at the transmitter, other than the addition of the CP there is no other change required in the transmitter signaling.
[0025] Using the CDMA+CP scheme of the present invention, different types of receivers can be employed since CDMA is used, for example, conventional rake receivers or equalizers can be used. If there is a need for a more advanced receiver that can efficiently combine the identical broadcast/multicast signals from the different cells/sectors, then a fast Fourier transform (FFT)/inverse fast Fourier (IFFT) receiver 600 as shown in FIG. 6 can be also be employed. The FFT/IFFT architecture receiver 600 allows for lower complexity combining and equalization of the long channel response that results from the combined channel across the different sectors/cells, which is made possible by the insertion of the CP. A FFT block 602 performs FFT on the received signal and provides the transformed signal to a frequency domain equalizer 604. Equalization algorithms that can be used include but are not limited to, linear, decision feedback and maximum likelihood as illustrative examples. An inverse FFT (IFFT) then performs IFFT on the normalized signal. Finally, demodulation of the signal is performed by a quadrature phase shift keying (QPSK)/16 quadrature amplitude modulation (QAM) demodulator 608 (QPSK/16 QAM).
[0026] Referring now to FIG. 7, there is shown a communication system 700 in accordance with one embodiment of the invention. Communication system 700 can comprise a cellular system including a plurality of cell sites 702-706 that can each broadcast/multicast messages. One or more of the cell sites can be arranged into different sectors in the system. A plurality of cellular telephones 708 and 710 operate within the system 700. The communication system 700 including the cellular telephones 708, 710 employ the CDMA+CP scheme of the present invention allowing for an enhanced broadcast multi-cast mode for HRPD that is backward compatible with existing CDMA systems.
[0027] In another embodiment of the invention, pilot symbols are inserted into the data fields for the broadcast/multicast messages. The pilot symbols can be code-domain (CD) or time-domain (TD) multiplexed. The position of the pilot symbols in the code or in the time domain can be arbitrary or optimized based on different criteria. The addition of the pilot symbols can be in addition to the CP previously described or using the pilot symbols alone without using the CP. In FIG. 8, there is shown a data field such as data field 302 previously shown, but in FIG. 8 a pilot 806 is added to the data 802 and CP 804. Pilot 806 can comprise a TD pilot, although shown added to the end of the data field; the TD pilot 806 can also be introduced at the beginning of the data field(s). In the illustrative example shown in FIG. 8, the pilot can be a TD pilot 806 having Np codes, the CP can have Nc, chips, the data field can for example have 400 chips and the entire data field shown in FIG. 8 can be a CDMA modulated data field comprising 400+Nc+Np chips. Since the pilot symbols are inserted in the data field, the pilot is also spread using the content-dependent long spreading code. These pilot symbols allow for simple (one shot) and efficient estimation of the composite broadcast/multicast channel (from multiple sectors).
[0028] In FIG. 9, there is shown an alternate embodiment in which a TD pilot 904 is added to the data 902 without the use of a CP. In the illustrative example shown in FIG. 9, the data 902 is transmitted without the use of long code spreading. In FIG. 10, another embodiment is shown were a code-division pilot 1002 (example having M codes) is added to the data 1004 (CDMA modulated data having 16-M codes). Using a pilot as discussed facilitates combining and equalization at the receivers that receive the broadcast or multicast transmissions sent out by a communication system. Combining and equalization of the composite long channel from all the cells/sectors can be accomplished efficiently using the previously discussed FFT/IFFT receiver architecture or other receiver architectures. When a pilot signal is added to the data as discussed, the pilot chips are known and can be utilized to remove the edge effects during equalization by the receiver(s).
[0029] In FIG. 11 there is shown a flowchart highlighting how a broadcast/multicast transmission is received. In 1102, the data fields are extracted from the rest of the transmitted packet. In 1104 the pilot is extracted from the data and channel estimation is performed. In 1106, the CP is removed if used in the transmission of the data field.
[0030] While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims. The concept of CDMA+CP transmission with content dependent spreading for broadcast/multicast can be applied in other systems besides the 3GPP High Speed Downlink Packet Access (HSDPA) system that was discussed.
