Orthogonal frequency division multiplexing¡]OFDM¡^systems play an important
role in modern wireless communications due to following advantages: bandwidth
saving¡Bcombat with frequency selective fading channel and high throughput. The
performance of wireless communications is often degraded by fading channel .
adaptive modulation and subcarrier allocation are proposed to overcome the degration
to meet the quality of servie¡]QoS¡^. Lagrange method and heuristics method, two of
the subcarrier allocation technology under multi-user OFDM, can achieve the goal
that maximizing bit rate with minimizing transmitted power. However, significantly
high complexity of either Lagrange method or heuristics method makes the
implementation difficult. Zhang and Letaief proposed a method of making subcarriers
detected one by one to reduce the complexity. However, in piratical, an OFDM system
accommodates hundred of , or even thousand of subcarriers, so the method can be
improved.
In this thesis, we propose a subcarrier allocation method. The users that are not
satisfied with the QOS requirement are named demander, and the users satisfied with
the QOS requirement are named supplier. In the proposed subcarrier allocation
method, we evaluate the number of subcarriers that demanders need and remove the
subcarriers from supplier to directly compensate demander. Then the system has
lower complexity due to less iterations.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0730110-020929 |
| Date | 30 July 2010 |
| Creators | Lin, Cheng-cheng |
| Contributors | Jieh-Chian Wu, Ju-Ya Chen, Ching-Piao Hung |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0730110-020929 |
| Rights | restricted, Copyright information available at source archive |
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