Apparatus and method for signal constitution for downlink of OFDMA-based cellular system

A downlink signal constitution apparatus, which is for a cellular system using an orthogonal frequency division multiplexing access method, the downlink signal constitution apparatus comprising:

• a first memory for storing traffic channel information of each user;
• a second memory for storing channel information, traffic requirement, and moving speed information of each user;
• a transmission user and transmission mode determiner for determining a transmission user and a transmission mode according to a defined method using the information stored in the second memory;
• a traffic channel processor for reading the traffic channel information stored in the first memory according to the transmission mode determined by the transmission user and transmission mode determiner, and performing coding, interleaving, and symbol-mapping of the traffic channel;
• an additional pilot symbol generator for generating additional pilot symbols necessary for a demodulation of the traffic channel, using the transmission mode determined by the transmission user and transmission mode determiner and the moving speed information stored in the second memory;
• a time/sub-carrier/antenna mapper for multiplying the traffic channel symbols output from the traffic channel processor and the additional pilot symbols output from the additional pilot symbol generator by a channel gain by channels/users, and mapping the resulting symbols to time, sub-carrier, and antenna by a defined method;
• a common/control channel processor for receiving common/control channel information, and performing coding, interleaving, and symbol-mapping of the received common/control channels;
• and
• a fundamental pilot symbol generator for generating a fundamental pilot symbol necessary for demodulation of the common/control channels.