Method for transmitting control information on the forward link of a wireless network
View Patent ↗A signaling method is provided that can improve the efficiency of forward-link control signaling in OFDM systems. The method involves using a set of forward-link subcarriers that are dedicated for control information, and are shared by a set of two or more users. The control information destined for each user is spread using a respective spreading code, thereby to provide a spread control message. The spread control messages destined for the various users are summed together prior to transmission.
1. A method, comprising:
generating control messages that are respectively destined for two or more users;
spreading each control message using a spreading code that is respectively associated with one of the users;
summing the spread control messages, thereby to form a composite control message;
in an OFDM transmitter in which a full range of subcarriers spanning an OFDM symbol is partitioned into a first plurality of subcarriers and a second plurality of subcarriers, mapping the composite control message to the first plurality of subcarriers, thereby to partially define one or more OFDM symbols, wherein the first plurality of subcarriers constitutes a common subchannel for signaling to the users;
in the OFDM transmitter, mapping one or more further messages to the second plurality of subcarriers, thereby to fully define the one or more OFDM symbols; and
transmitting the OFDM symbol or symbols.
2. The method of claim 1 , wherein the spreading codes are Walsh codes.
3. The method of claim 1 , wherein the spreading codes are PN sequences.
4. The method of claim 1 , wherein, the spreading codes are products of Walsh codes with PN sequences.
5. The method of claim 1 , further comprising, for at least one user, identifying a subchannel that, has been assigned to said user for making reverse-link transmissions thereon, and wherein the spreading of at least one message to said user is performed using a spreading code associated with said assigned subchannel.
6. A method to be performed at a user terminal, comprising:
receiving an OFDM symbol from a base station on a range of subcarriers that span the OFDM symbol; recovering from the OFDM symbol an OFDM control message received on a common plurality of subcarriers used by the base station for signalling to users, wherein the common plurality constitutes less than the full range of subcarriers that span the OFDM symbol; despreading the control message using a despreading code effective for removing from a composite message such messages as are destined for other users;, and decoding the despread control message.
7. The method of claim 6 , wherein the despreading code is equivalent to a Walsh code.
8. The method of claim 6 , wherein the despreading code is equivalent to a PN sequence.
9. The method of claim 6 , wherein the despreading code is equivalent to a product of a Walsh code with a PN sequence.
10. The method of claim 6 , further comprising selecting the despreading code as that code which is associated with a subchannel that has been assigned to said user terminal for making reverse-link transmissions thereon.