Abstract:
A method for iteratively decoding a block turbo code includes: receiving a signal frame formed of a product code obtained by serially concatenating block codes; forming a reliability array for signal demodulation and initializing extrinsic reliability information; performing a complexity-reduced soft decision output Viterbi decoding algorithm for all of the codewords existing on a current axis and calculating extrinsic reliability using soft decision output information output as a result of the decoding; checking whether an iterative decoding completion condition is satisfied, and outputting a decoded value and terminating an iterative decoding process when the condition is satisfied; and normalizing reliability information when the condition is not satisfied, performing reliability equalization, and repeating the decoding process for a next axis.
Abstract:
Provided is a method and apparatus for common packet channel access to transmit data packet from a mobile terminal to a satellite access network in a mobile satellite communication system. The method and apparatus of this invention reduces transmission delay time, enhances the probability of successful access, and controls the currently used common packet channel by using a common control channel broadcast by the satellite access network. The method includes the steps of: receiving an access preamble including an access signature code and a collision-detection preamble including a collision-detection signature code, which are transmitted together from a plurality of mobile terminals, and transmitting an acknowledgement to the access preamble and collision-detection preamble to mobile terminals through a preamble acknowledgement channel.
Abstract:
PURPOSE: A device for controlling a closed loop power in a satellite mobile communication system and a method therefor are provided to previously calculate a power error after a loop delay time by using a pilot channel for downlink power control and to generate a power control command based on the calculated power error. CONSTITUTION: A converter(110) converts a power control command received from a base station into a power control width. A loop delay compensator(120) outputs a final power control width including a channel change after a loop delay for the received power control width. A channel change measurer(130) receives power of a pilot channel, and measures a channel change. A tab coefficient generator(140) generates a tab coefficient of the loop delay compensator(120) by using the channel change of the power of the pilot channel and a frequency of power control.
Abstract:
PURPOSE: A method for transmitting an adaptive packet in a cellular phone mobile communication system by using a multi beam satellite is provided to select a sector/beam requesting a minimal power, and to select a wireless resource of a transmission frame, then to assign a minimal power requested to satisfy packet reception quality by using a transmission path gain estimated for each user, thereby minimizing interference in other packet transmissions. CONSTITUTION: A system updates an active beam set for each user(501), and updates transmission path gains for each user based on an RSSI of a reported pilot signal(502). The system sets priorities for packets included in headers of transmission queues of each service(503). The system decides whether packets are to be assigned(504). If so, the system assigns packets for a reserved assignment service by a reserved assignment system(506), and assigns packets for a sharing assignment service by a sharing assignment system(510). If the packet assignment is successful, the system removes packets corresponding to an assigned transmission(509). If the packets fail in the assignment by the sharing assignment system, the system does not attempt assigning the packets(512).
Abstract:
PURPOSE: A method for adaptively transmitting a signal in a wireless communication system and an apparatus therefor are provided to vary a transmission parameter of the signal according to an attenuation state of a communication channel. CONSTITUTION: An attenuation quantity estimator(15) estimates a channel attenuation quantity of a wireless communication channel. A control quantity decider(16) sets a coding rate, a modulation level, and a transmission power of a signal to be transmitted on the basis of the estimated channel estimation quantity. An encoder(12) encodes the signal according to the set coding rate. A modulator(13) modulates the signal according to the set modulation level. A power controller(14) transmits the encoded and modulated signal according to the set transmission power.
Abstract:
PURPOSE: A method for connecting an optional access channel in a satellite mobile communication system and a method therefor are provided to easily synchronize a mobile station with a satellite system, and to distributively transmit preambles and message data, thereby reducing interferences between packet signals. CONSTITUTION: A mobile station selects an optional channel access service class(S801), and initializes a retransmission period counter to '0'(S803). If the counter exceeds a maximum retransmission period(S805), an access procedure fails(S807). If the counter does not exceed the maximum retransmission period, the mobile station updates a parameter related to an optional access channel(S809). The mobile station checks persistence(S811), and initializes a power increase retransmission period for transmitting preambles and message data to '0'(S815). If a power increase counter is smaller than a maximum power increase retransmission period(S817), the mobile station selects a signature(S823), and transmits the preambles and the message data(S825). If a detected value is '1'(S827), the mobile station completes an optional access channel process.
Abstract:
PURPOSE: A reiterative decoding method of a block turbo code and a decoding medium for storing a program thereof are provided to reduce the complexity and perform a reiterative decoding process by using a soft output Viterbi decoding algorithm. CONSTITUTION: A signal frame is received from a transmission end(S1). A reliability array is formed to demodulate a signal after the signal frame is received from the transmission end(S2-S4). A soft output Viterbi decoding algorithm for all codewords is performed(S5). The external reliability is calculated by using the soft decision output information generated from the soft output Viterbi decoding algorithm(S6,S7). A decoding value is outputted and a reiterative decoding process is finished if the external reliability satisfies a reiterative decoding end condition(S9,S10). The reliability information is normalized, a reliability normal process is performed if the external reliability does not satisfy the reiterative decoding end condition(S11-S17).
Abstract:
PURPOSE: A method for adaptively transmitting a signal in a wireless communication system and an apparatus therefor are provided to vary a transmission parameter of the signal according to an attenuation state of a communication channel. CONSTITUTION: An attenuation quantity estimator(15) estimates a channel attenuation quantity of a wireless communication channel. A control quantity decider(16) sets a coding rate, a modulation level, and a transmission power of a signal to be transmitted on the basis of the estimated channel estimation quantity. An encoder(12) encodes the signal according to the set coding rate. A modulator(13) modulates the signal according to the set modulation level. A power controller(14) transmits the encoded and modulated signal according to the set transmission power.
Abstract:
PURPOSE: A turbo coding method using a soft output Viterbi algorithm with a reduced complexity is provided to reduce complexity by using metrics in carrying out a turbo code of a block code using the soft output Viterbi decoding, and accordingly easily implement the turbo code of the block code with a desired complexity by effectively calculating a soft output value. CONSTITUTION: A block code is configured at a transmitting end in a first step. A decoding is carried out by rows using the soft output Viterbi algorithm with a reduced complexity regarding to a frame received at a receiving end in the second step. A decoding is carried out by lines using the soft output Viterbi algorithm with a reduced complexity by adding a soft output information outputted from the decoding by rows in a third step. A turbo code is carried out in the second step by adding a soft output information outputted from the decoding by lines in the third step.
Abstract:
PURPOSE: A method for calculating a bit error rate in a nonlinear satellite communication channel is provided to calculate the bit error rate exactly by using a quasi-analytic simulation technique. CONSTITUTION: A transmit filter(12) filters a transmit signal of a transmit modulator(11), and a nonlinear amplifier(13) receives an output of the transmit filter(12). A demodulator(15) demodulates an output of the nonlinear amplifier(13) through a receipt filter(14). At this time, a forward link noise is included in a forward link between the transmit filter(12) and the nonlinear amplifier(13), and a backward link noise is included in a backward link between the nonlinear amplifier(13) and the receipt filter(14). Each of a probability density function about the forward link noise and a probability density function about the backward link noise are calculated at an input terminal and an output terminal of the nonlinear amplifier(13). Next, A bit error rate of a receipt terminal is calculated by using two probability density functions through a quasi-analytic simulation technique. In the quasi-analytic simulation technique, the bit error rate is calculated on the basis of a mean of a conditional error probability about a signal sample received through the receipt terminal.