Transmission method of mobile station for random access channel diversity
View Patent ↗A transmission method performed by a mobile station for random access channel (RACH) burst transmission diversity gain is provided. According to the method, by combining and using switching diversity by beam forming, frequency hopping, and power ramping, the probability that when the speed of a mobile station is low, the mobile station falls into a deep fading environment is lowered, thereby increasing the probability of detecting an RACH signature of the base station. Also, by using the transmission parameters (subbands, precoding matrixes, power, etc.) which are used for successful transmission of an RACH burst, for transmission of a successive user packet data, reliable transmission of the successive user packet data can be performed.
1. A transmission method performed by a mobile station of obtaining random access diversity, the method comprising:
(a) processing the signal of a random access channel (RACH) burst according to a beam forming pattern set from among a plurality of beam forming patterns, and then, transmitting the RACH burst to a base station with a first transmission power through multiple transmission antennas;
(b) if a non-acknowledgement (NACK) response to the RACH burst from the base station is received, newly setting a beam forming pattern which is different from the set beam forming pattern, to a new RACH burst, and then, returning to the step (a); and
(c) if an acknowledgement (ACK) response to the RACH burst is received from the base station, transmitting user packet data in response to the received ACK response using the same beam forming pattern set used to transmit the RACH burst,
wherein the user packet data transmitted in response to the received ACK response is transmitted with a transmission power determined based on at least one of a structure of a preamble of the RACH burst, a modulation scheme, a coding scheme, and a size of preamble of the packet data, and
wherein the transmission power is determined in the mobile station according to the first transmission power, first and second estimated signal-to-noise ratio values respectively required for the RACH burst and the user packet data to be received successfully, and a marginal power accounting for any changes in channel characteristics.
2. The method of claim 1 , wherein the RACH burst is transmitted by using a subband that is different from a subband allocated to the previous RACH burst.
3. The method of claim 1 , further comprising,
(d) if a NACK from the base station is received while a predetermined time has elapsed, newly setting a transmission power higher than an previously set transmission power and returning to the step (a).
4. The method of claim 1 , wherein in the step (c), a user packet data is transmitted by using a subband in which the RACH burst, of which the ACK is received, is transmitted.
5. The method of claim 1 , wherein the step (a) comprises:
(a1) generating the RACH burst signal, by performing orthogonal frequency division multiple access (OFDMA) modulation of the RACH burst so that the RACH burst can be loaded on a set subband; and
(a2) processing the RACH burst signal according to the set beam forming pattern, and transmitting the RACH burst signal.
6. The method of claim 5 , wherein the step (a2) comprises:
processing the RACH burst signal, by applying a precoding matrix corresponding to the set beam forming pattern, to the RACH burst signal; and
amplifying and up-converting each component of the processed RACH burst signal, and then, transmitting the component to a corresponding antenna from among the multiple transmission antennas.
7. The method of claim 1 , wherein the RACH burst includes a signature sequence for identifying a mobile station which attempts random access.
8. The method of claim 1 , wherein the RACH burst includes information on at least one of a user identifier and a resource request for setting up a call.
9. The method of claim 5 , wherein the OFDMA modulation includes discrete Fourier transform-spread (DFT S) OFDMA modulation.
10. A non-transitory computer readable recording medium having embodied thereon a computer program for executing the method of claim 1 .
11. A transmission method performed by a mobile station of obtaining random access diversity, the method comprising:
(a) processing the signal of a random access channel (RACH) burst according to a beam forming pattern set from among a plurality of beam forming patterns, and then, transmitting the RACH burst to a base station with a first transmission power through multiple transmission antennas;
(b) if a non-acknowledgement (NACK) response to the RACH burst from the base station is received, newly setting a beam forming pattern which is different from the set beam forming pattern, to a new RACH burst, and then, returning to the step (a); and
(c) if an acknowledgement (ACK) response to the RACH burst is received from the base station, transmitting user packet data in response to the received ACK response using the same beam forming pattern set used to transmit the RACH burst,
wherein the user packet data transmitted in response to the received ACK response is transmitted with a transmission power determined in the mobile station according to the first transmission power, and first and second estimated signal-to-noise ratio values respectively required for the RACH burst and the user packet data to be received successfully and a marginal power accounting for any changes in channel characteristics.
12. The method of claim 11 , wherein the transmission power of the user packet data P 2 is determined based on the equation:
P 2 =P 1 *10^{( SNR 2 − SNR 1 +Δ SNR )/10}
where P 1 is the first transmission power, SNR 1 and SNR 2 respectively are the first and second signal-to-noise ratio values, and ΔSNR is a marginal power accounting for any changes in channel characteristics.