Multiuser OFDM with adaptive subcarrier, bit, and power allocation

摘要

Multiuser orthogonal frequency division multiplexing (OFDM) withnadaptive multiuser subcarrier allocation and adaptive modulation isnconsidered. Assuming knowledge of the instantaneous channel gains fornall users, we propose a multiuser OFDM subcarrier, bit, and powernallocation algorithm to minimize the total transmit power. This is donenby assigning each user a set of subcarriers and by determining thennumber of bits and the transmit power level for each subcarrier. Wenobtain the performance of our proposed algorithm in a multiusernfrequency selective fading environment for various time delay spreadnvalues and various numbers of users. The results show that our proposednalgorithm outperforms multiuser OFDM systems with static time-divisionnmultiple access (TDMA) or frequency-division multiple access (FDMA)ntechniques which employ fixed and predetermined time-slot or subcarriernallocation schemes. We have also quantified the improvement in terms ofnthe overall required transmit power, the bit-error rate (BER), or thenarea of coverage for a given outage probability